Calculus Examples

$f (x) = 2 x^{2} \cos (6 x)$

Step 1

Find the first derivative.

Tap for more steps...

Step 1.1

Since $2$ is constant with respect to $x$ , the derivative of $2 x^{2} \cos (6 x)$ with respect to $x$ is $2 \frac{d}{d x} [x^{2} \cos (6 x)]$ .

$2 \frac{d}{d x} [x^{2} \cos (6 x)]$

Step 1.2

Differentiate using the Product Rule which states that $\frac{d}{d x} [f (x) g (x)]$ is $f (x) \frac{d}{d x} [g (x)] + g (x) \frac{d}{d x} [f (x)]$ where $f (x) = x^{2}$ and $g (x) = \cos (6 x)$ .

$2 (x^{2} \frac{d}{d x} [\cos (6 x)] + \cos (6 x) \frac{d}{d x} [x^{2}])$

Step 1.3

Differentiate using the chain rule, which states that $\frac{d}{d x} [f (g (x))]$ is $f' (g (x)) g' (x)$ where $f (x) = \cos (x)$ and $g (x) = 6 x$ .

Tap for more steps...

Step 1.3.1

To apply the Chain Rule, set $u$ as $6 x$ .

$2 (x^{2} (\frac{d}{d u} [\cos (u)] \frac{d}{d x} [6 x]) + \cos (6 x) \frac{d}{d x} [x^{2}])$

Step 1.3.2

The derivative of $\cos (u)$ with respect to $u$ is $- \sin (u)$ .

$2 (x^{2} (- \sin (u) \frac{d}{d x} [6 x]) + \cos (6 x) \frac{d}{d x} [x^{2}])$

Step 1.3.3

Replace all occurrences of $u$ with $6 x$ .

$2 (x^{2} (- \sin (6 x) \frac{d}{d x} [6 x]) + \cos (6 x) \frac{d}{d x} [x^{2}])$

Step 1.4

Differentiate.

Tap for more steps...

Step 1.4.1

Since $6$ is constant with respect to $x$ , the derivative of $6 x$ with respect to $x$ is $6 \frac{d}{d x} [x]$ .

$2 (x^{2} (- \sin (6 x) (6 \frac{d}{d x} [x])) + \cos (6 x) \frac{d}{d x} [x^{2}])$

Step 1.4.2

Multiply $6$ by $- 1$ .

$2 (x^{2} (- 6 \sin (6 x) \frac{d}{d x} [x]) + \cos (6 x) \frac{d}{d x} [x^{2}])$

Step 1.4.3

Differentiate using the Power Rule which states that $\frac{d}{d x} [x^{n}]$ is $n x^{n - 1}$ where $n = 1$ .

$2 (x^{2} (- 6 \sin (6 x) \cdot 1) + \cos (6 x) \frac{d}{d x} [x^{2}])$

Step 1.4.4

Multiply $- 6$ by $1$ .

$2 (x^{2} (- 6 \sin (6 x)) + \cos (6 x) \frac{d}{d x} [x^{2}])$

Step 1.4.5

Differentiate using the Power Rule which states that $\frac{d}{d x} [x^{n}]$ is $n x^{n - 1}$ where $n = 2$ .

$2 (x^{2} (- 6 \sin (6 x)) + \cos (6 x) (2 x))$

Step 1.5

Simplify.

Tap for more steps...

Step 1.5.1

Apply the distributive property.

$2 (x^{2} (- 6 \sin (6 x))) + 2 (\cos (6 x) (2 x))$

Step 1.5.2

Combine terms.

Tap for more steps...

Step 1.5.2.1

Multiply $- 6$ by $2$ .

$- 12 (x^{2} (\sin (6 x))) + 2 (\cos (6 x) (2 x))$

Step 1.5.2.2

Multiply $2$ by $2$ .

$- 12 x^{2} \sin (6 x) + 4 \cos (6 x) x$

Step 1.5.3

Reorder terms.

$f' (x) = - 12 x^{2} \sin (6 x) + 4 x \cos (6 x)$

Step 2

Find the second derivative.

Tap for more steps...

Step 2.1

By the Sum Rule, the derivative of $- 12 x^{2} \sin (6 x) + 4 x \cos (6 x)$ with respect to $x$ is $\frac{d}{d x} [- 12 x^{2} \sin (6 x)] + \frac{d}{d x} [4 x \cos (6 x)]$ .

$\frac{d}{d x} [- 12 x^{2} \sin (6 x)] + \frac{d}{d x} [4 x \cos (6 x)]$

Step 2.2

Evaluate $\frac{d}{d x} [- 12 x^{2} \sin (6 x)]$ .

Tap for more steps...

Step 2.2.1

Since $- 12$ is constant with respect to $x$ , the derivative of $- 12 x^{2} \sin (6 x)$ with respect to $x$ is $- 12 \frac{d}{d x} [x^{2} \sin (6 x)]$ .

$- 12 \frac{d}{d x} [x^{2} \sin (6 x)] + \frac{d}{d x} [4 x \cos (6 x)]$

Step 2.2.2

Differentiate using the Product Rule which states that $\frac{d}{d x} [f (x) g (x)]$ is $f (x) \frac{d}{d x} [g (x)] + g (x) \frac{d}{d x} [f (x)]$ where $f (x) = x^{2}$ and $g (x) = \sin (6 x)$ .

$- 12 (x^{2} \frac{d}{d x} [\sin (6 x)] + \sin (6 x) \frac{d}{d x} [x^{2}]) + \frac{d}{d x} [4 x \cos (6 x)]$

Step 2.2.3

Differentiate using the chain rule, which states that $\frac{d}{d x} [f (g (x))]$ is $f' (g (x)) g' (x)$ where $f (x) = \sin (x)$ and $g (x) = 6 x$ .

Tap for more steps...

Step 2.2.3.1

To apply the Chain Rule, set $u_{1}$ as $6 x$ .

$- 12 (x^{2} (\frac{d}{d u_{1}} [\sin (u_{1})] \frac{d}{d x} [6 x]) + \sin (6 x) \frac{d}{d x} [x^{2}]) + \frac{d}{d x} [4 x \cos (6 x)]$

Step 2.2.3.2

The derivative of $\sin (u_{1})$ with respect to $u_{1}$ is $\cos (u_{1})$ .

$- 12 (x^{2} (\cos (u_{1}) \frac{d}{d x} [6 x]) + \sin (6 x) \frac{d}{d x} [x^{2}]) + \frac{d}{d x} [4 x \cos (6 x)]$

Step 2.2.3.3

Replace all occurrences of $u_{1}$ with $6 x$ .

$- 12 (x^{2} (\cos (6 x) \frac{d}{d x} [6 x]) + \sin (6 x) \frac{d}{d x} [x^{2}]) + \frac{d}{d x} [4 x \cos (6 x)]$

Step 2.2.4

Since $6$ is constant with respect to $x$ , the derivative of $6 x$ with respect to $x$ is $6 \frac{d}{d x} [x]$ .

$- 12 (x^{2} (\cos (6 x) (6 \frac{d}{d x} [x])) + \sin (6 x) \frac{d}{d x} [x^{2}]) + \frac{d}{d x} [4 x \cos (6 x)]$

Step 2.2.5

Differentiate using the Power Rule which states that $\frac{d}{d x} [x^{n}]$ is $n x^{n - 1}$ where $n = 1$ .

$- 12 (x^{2} (\cos (6 x) (6 \cdot 1)) + \sin (6 x) \frac{d}{d x} [x^{2}]) + \frac{d}{d x} [4 x \cos (6 x)]$

Step 2.2.6

Differentiate using the Power Rule which states that $\frac{d}{d x} [x^{n}]$ is $n x^{n - 1}$ where $n = 2$ .

$- 12 (x^{2} (\cos (6 x) (6 \cdot 1)) + \sin (6 x) (2 x)) + \frac{d}{d x} [4 x \cos (6 x)]$

Step 2.2.7

Multiply $6$ by $1$ .

$- 12 (x^{2} (\cos (6 x) \cdot 6) + \sin (6 x) (2 x)) + \frac{d}{d x} [4 x \cos (6 x)]$

Step 2.2.8

Move $6$ to the left of $\cos (6 x)$ .

$- 12 (x^{2} (6 \cos (6 x)) + \sin (6 x) (2 x)) + \frac{d}{d x} [4 x \cos (6 x)]$

Step 2.3

Evaluate $\frac{d}{d x} [4 x \cos (6 x)]$ .

Tap for more steps...

Step 2.3.1

Since $4$ is constant with respect to $x$ , the derivative of $4 x \cos (6 x)$ with respect to $x$ is $4 \frac{d}{d x} [x \cos (6 x)]$ .

$- 12 (x^{2} (6 \cos (6 x)) + \sin (6 x) (2 x)) + 4 \frac{d}{d x} [x \cos (6 x)]$

Step 2.3.2

Differentiate using the Product Rule which states that $\frac{d}{d x} [f (x) g (x)]$ is $f (x) \frac{d}{d x} [g (x)] + g (x) \frac{d}{d x} [f (x)]$ where $f (x) = x$ and $g (x) = \cos (6 x)$ .

$- 12 (x^{2} (6 \cos (6 x)) + \sin (6 x) (2 x)) + 4 (x \frac{d}{d x} [\cos (6 x)] + \cos (6 x) \frac{d}{d x} [x])$

Step 2.3.3

Differentiate using the chain rule, which states that $\frac{d}{d x} [f (g (x))]$ is $f' (g (x)) g' (x)$ where $f (x) = \cos (x)$ and $g (x) = 6 x$ .

Tap for more steps...

Step 2.3.3.1

To apply the Chain Rule, set $u_{2}$ as $6 x$ .

$- 12 (x^{2} (6 \cos (6 x)) + \sin (6 x) (2 x)) + 4 (x (\frac{d}{d u_{2}} [\cos (u_{2})] \frac{d}{d x} [6 x]) + \cos (6 x) \frac{d}{d x} [x])$

Step 2.3.3.2

The derivative of $\cos (u_{2})$ with respect to $u_{2}$ is $- \sin (u_{2})$ .

$- 12 (x^{2} (6 \cos (6 x)) + \sin (6 x) (2 x)) + 4 (x (- \sin (u_{2}) \frac{d}{d x} [6 x]) + \cos (6 x) \frac{d}{d x} [x])$

Step 2.3.3.3

Replace all occurrences of $u_{2}$ with $6 x$ .

$- 12 (x^{2} (6 \cos (6 x)) + \sin (6 x) (2 x)) + 4 (x (- \sin (6 x) \frac{d}{d x} [6 x]) + \cos (6 x) \frac{d}{d x} [x])$

Step 2.3.4

Since $6$ is constant with respect to $x$ , the derivative of $6 x$ with respect to $x$ is $6 \frac{d}{d x} [x]$ .

$- 12 (x^{2} (6 \cos (6 x)) + \sin (6 x) (2 x)) + 4 (x (- \sin (6 x) (6 \frac{d}{d x} [x])) + \cos (6 x) \frac{d}{d x} [x])$

Step 2.3.5

Differentiate using the Power Rule which states that $\frac{d}{d x} [x^{n}]$ is $n x^{n - 1}$ where $n = 1$ .

$- 12 (x^{2} (6 \cos (6 x)) + \sin (6 x) (2 x)) + 4 (x (- \sin (6 x) (6 \cdot 1)) + \cos (6 x) \frac{d}{d x} [x])$

Step 2.3.6

Differentiate using the Power Rule which states that $\frac{d}{d x} [x^{n}]$ is $n x^{n - 1}$ where $n = 1$ .

$- 12 (x^{2} (6 \cos (6 x)) + \sin (6 x) (2 x)) + 4 (x (- \sin (6 x) (6 \cdot 1)) + \cos (6 x) \cdot 1)$

Step 2.3.7

Multiply $6$ by $1$ .

$- 12 (x^{2} (6 \cos (6 x)) + \sin (6 x) (2 x)) + 4 (x (- \sin (6 x) \cdot 6) + \cos (6 x) \cdot 1)$

Step 2.3.8

Multiply $6$ by $- 1$ .

$- 12 (x^{2} (6 \cos (6 x)) + \sin (6 x) (2 x)) + 4 (x (- 6 \sin (6 x)) + \cos (6 x) \cdot 1)$

Step 2.3.9

Multiply $\cos (6 x)$ by $1$ .

$- 12 (x^{2} (6 \cos (6 x)) + \sin (6 x) (2 x)) + 4 (x (- 6 \sin (6 x)) + \cos (6 x))$

Step 2.4

Simplify.

Tap for more steps...

Step 2.4.1

Apply the distributive property.

$- 12 (x^{2} (6 \cos (6 x))) - 12 (\sin (6 x) (2 x)) + 4 (x (- 6 \sin (6 x)) + \cos (6 x))$

Step 2.4.2

Apply the distributive property.

$- 12 (x^{2} (6 \cos (6 x))) - 12 (\sin (6 x) (2 x)) + 4 (x (- 6 \sin (6 x))) + 4 \cos (6 x)$

Step 2.4.3

Combine terms.

Tap for more steps...

Step 2.4.3.1

Multiply $6$ by $- 12$ .

$- 72 (x^{2} (\cos (6 x))) - 12 (\sin (6 x) (2 x)) + 4 (x (- 6 \sin (6 x))) + 4 \cos (6 x)$

Step 2.4.3.2

Multiply $2$ by $- 12$ .

$- 72 x^{2} \cos (6 x) - 24 (\sin (6 x) (x)) + 4 (x (- 6 \sin (6 x))) + 4 \cos (6 x)$

Step 2.4.3.3

Multiply $- 6$ by $4$ .

$- 72 x^{2} \cos (6 x) - 24 \sin (6 x) x - 24 (x (\sin (6 x))) + 4 \cos (6 x)$

Step 2.4.3.4

Subtract $24 x \sin (6 x)$ from $- 24 \sin (6 x) x$ .

Tap for more steps...

Step 2.4.3.4.1

Move $\sin (6 x)$ .

$- 72 x^{2} \cos (6 x) - 24 x \sin (6 x) - 24 x \sin (6 x) + 4 \cos (6 x)$

Step 2.4.3.4.2

Subtract $24 x \sin (6 x)$ from $- 24 x \sin (6 x)$ .

$f'' (x) = - 72 x^{2} \cos (6 x) - 48 x \sin (6 x) + 4 \cos (6 x)$

Step 3

Find the third derivative.

Tap for more steps...

Step 3.1

By the Sum Rule, the derivative of $- 72 x^{2} \cos (6 x) - 48 x \sin (6 x) + 4 \cos (6 x)$ with respect to $x$ is $\frac{d}{d x} [- 72 x^{2} \cos (6 x)] + \frac{d}{d x} [- 48 x \sin (6 x)] + \frac{d}{d x} [4 \cos (6 x)]$ .

$\frac{d}{d x} [- 72 x^{2} \cos (6 x)] + \frac{d}{d x} [- 48 x \sin (6 x)] + \frac{d}{d x} [4 \cos (6 x)]$

Step 3.2

Evaluate $\frac{d}{d x} [- 72 x^{2} \cos (6 x)]$ .

Tap for more steps...

Step 3.2.1

Since $- 72$ is constant with respect to $x$ , the derivative of $- 72 x^{2} \cos (6 x)$ with respect to $x$ is $- 72 \frac{d}{d x} [x^{2} \cos (6 x)]$ .

$- 72 \frac{d}{d x} [x^{2} \cos (6 x)] + \frac{d}{d x} [- 48 x \sin (6 x)] + \frac{d}{d x} [4 \cos (6 x)]$

Step 3.2.2

Differentiate using the Product Rule which states that $\frac{d}{d x} [f (x) g (x)]$ is $f (x) \frac{d}{d x} [g (x)] + g (x) \frac{d}{d x} [f (x)]$ where $f (x) = x^{2}$ and $g (x) = \cos (6 x)$ .

$- 72 (x^{2} \frac{d}{d x} [\cos (6 x)] + \cos (6 x) \frac{d}{d x} [x^{2}]) + \frac{d}{d x} [- 48 x \sin (6 x)] + \frac{d}{d x} [4 \cos (6 x)]$

Step 3.2.3

Differentiate using the chain rule, which states that $\frac{d}{d x} [f (g (x))]$ is $f' (g (x)) g' (x)$ where $f (x) = \cos (x)$ and $g (x) = 6 x$ .

Tap for more steps...

Step 3.2.3.1

To apply the Chain Rule, set $u_{1}$ as $6 x$ .

$- 72 (x^{2} (\frac{d}{d u_{1}} [\cos (u_{1})] \frac{d}{d x} [6 x]) + \cos (6 x) \frac{d}{d x} [x^{2}]) + \frac{d}{d x} [- 48 x \sin (6 x)] + \frac{d}{d x} [4 \cos (6 x)]$

Step 3.2.3.2

The derivative of $\cos (u_{1})$ with respect to $u_{1}$ is $- \sin (u_{1})$ .

$- 72 (x^{2} (- \sin (u_{1}) \frac{d}{d x} [6 x]) + \cos (6 x) \frac{d}{d x} [x^{2}]) + \frac{d}{d x} [- 48 x \sin (6 x)] + \frac{d}{d x} [4 \cos (6 x)]$

Step 3.2.3.3

Replace all occurrences of $u_{1}$ with $6 x$ .

$- 72 (x^{2} (- \sin (6 x) \frac{d}{d x} [6 x]) + \cos (6 x) \frac{d}{d x} [x^{2}]) + \frac{d}{d x} [- 48 x \sin (6 x)] + \frac{d}{d x} [4 \cos (6 x)]$

Step 3.2.4

Since $6$ is constant with respect to $x$ , the derivative of $6 x$ with respect to $x$ is $6 \frac{d}{d x} [x]$ .

$- 72 (x^{2} (- \sin (6 x) (6 \frac{d}{d x} [x])) + \cos (6 x) \frac{d}{d x} [x^{2}]) + \frac{d}{d x} [- 48 x \sin (6 x)] + \frac{d}{d x} [4 \cos (6 x)]$

Step 3.2.5

Differentiate using the Power Rule which states that $\frac{d}{d x} [x^{n}]$ is $n x^{n - 1}$ where $n = 1$ .

$- 72 (x^{2} (- \sin (6 x) (6 \cdot 1)) + \cos (6 x) \frac{d}{d x} [x^{2}]) + \frac{d}{d x} [- 48 x \sin (6 x)] + \frac{d}{d x} [4 \cos (6 x)]$

Step 3.2.6

Differentiate using the Power Rule which states that $\frac{d}{d x} [x^{n}]$ is $n x^{n - 1}$ where $n = 2$ .

$- 72 (x^{2} (- \sin (6 x) (6 \cdot 1)) + \cos (6 x) (2 x)) + \frac{d}{d x} [- 48 x \sin (6 x)] + \frac{d}{d x} [4 \cos (6 x)]$

Step 3.2.7

Multiply $6$ by $1$ .

$- 72 (x^{2} (- \sin (6 x) \cdot 6) + \cos (6 x) (2 x)) + \frac{d}{d x} [- 48 x \sin (6 x)] + \frac{d}{d x} [4 \cos (6 x)]$

Step 3.2.8

Multiply $6$ by $- 1$ .

$- 72 (x^{2} (- 6 \sin (6 x)) + \cos (6 x) (2 x)) + \frac{d}{d x} [- 48 x \sin (6 x)] + \frac{d}{d x} [4 \cos (6 x)]$

Step 3.3

Evaluate $\frac{d}{d x} [- 48 x \sin (6 x)]$ .

Tap for more steps...

Step 3.3.1

Since $- 48$ is constant with respect to $x$ , the derivative of $- 48 x \sin (6 x)$ with respect to $x$ is $- 48 \frac{d}{d x} [x \sin (6 x)]$ .

$- 72 (x^{2} (- 6 \sin (6 x)) + \cos (6 x) (2 x)) - 48 \frac{d}{d x} [x \sin (6 x)] + \frac{d}{d x} [4 \cos (6 x)]$

Step 3.3.2

Differentiate using the Product Rule which states that $\frac{d}{d x} [f (x) g (x)]$ is $f (x) \frac{d}{d x} [g (x)] + g (x) \frac{d}{d x} [f (x)]$ where $f (x) = x$ and $g (x) = \sin (6 x)$ .

$- 72 (x^{2} (- 6 \sin (6 x)) + \cos (6 x) (2 x)) - 48 (x \frac{d}{d x} [\sin (6 x)] + \sin (6 x) \frac{d}{d x} [x]) + \frac{d}{d x} [4 \cos (6 x)]$

Step 3.3.3

Differentiate using the chain rule, which states that $\frac{d}{d x} [f (g (x))]$ is $f' (g (x)) g' (x)$ where $f (x) = \sin (x)$ and $g (x) = 6 x$ .

Tap for more steps...

Step 3.3.3.1

To apply the Chain Rule, set $u_{2}$ as $6 x$ .

$- 72 (x^{2} (- 6 \sin (6 x)) + \cos (6 x) (2 x)) - 48 (x (\frac{d}{d u_{2}} [\sin (u_{2})] \frac{d}{d x} [6 x]) + \sin (6 x) \frac{d}{d x} [x]) + \frac{d}{d x} [4 \cos (6 x)]$

Step 3.3.3.2

The derivative of $\sin (u_{2})$ with respect to $u_{2}$ is $\cos (u_{2})$ .

$- 72 (x^{2} (- 6 \sin (6 x)) + \cos (6 x) (2 x)) - 48 (x (\cos (u_{2}) \frac{d}{d x} [6 x]) + \sin (6 x) \frac{d}{d x} [x]) + \frac{d}{d x} [4 \cos (6 x)]$

Step 3.3.3.3

Replace all occurrences of $u_{2}$ with $6 x$ .

$- 72 (x^{2} (- 6 \sin (6 x)) + \cos (6 x) (2 x)) - 48 (x (\cos (6 x) \frac{d}{d x} [6 x]) + \sin (6 x) \frac{d}{d x} [x]) + \frac{d}{d x} [4 \cos (6 x)]$

Step 3.3.4

Since $6$ is constant with respect to $x$ , the derivative of $6 x$ with respect to $x$ is $6 \frac{d}{d x} [x]$ .

$- 72 (x^{2} (- 6 \sin (6 x)) + \cos (6 x) (2 x)) - 48 (x (\cos (6 x) (6 \frac{d}{d x} [x])) + \sin (6 x) \frac{d}{d x} [x]) + \frac{d}{d x} [4 \cos (6 x)]$

Step 3.3.5

Differentiate using the Power Rule which states that $\frac{d}{d x} [x^{n}]$ is $n x^{n - 1}$ where $n = 1$ .

$- 72 (x^{2} (- 6 \sin (6 x)) + \cos (6 x) (2 x)) - 48 (x (\cos (6 x) (6 \cdot 1)) + \sin (6 x) \frac{d}{d x} [x]) + \frac{d}{d x} [4 \cos (6 x)]$

Step 3.3.6

Differentiate using the Power Rule which states that $\frac{d}{d x} [x^{n}]$ is $n x^{n - 1}$ where $n = 1$ .

$- 72 (x^{2} (- 6 \sin (6 x)) + \cos (6 x) (2 x)) - 48 (x (\cos (6 x) (6 \cdot 1)) + \sin (6 x) \cdot 1) + \frac{d}{d x} [4 \cos (6 x)]$

Step 3.3.7

Multiply $6$ by $1$ .

$- 72 (x^{2} (- 6 \sin (6 x)) + \cos (6 x) (2 x)) - 48 (x (\cos (6 x) \cdot 6) + \sin (6 x) \cdot 1) + \frac{d}{d x} [4 \cos (6 x)]$

Step 3.3.8

Move $6$ to the left of $\cos (6 x)$ .

$- 72 (x^{2} (- 6 \sin (6 x)) + \cos (6 x) (2 x)) - 48 (x (6 \cdot \cos (6 x)) + \sin (6 x) \cdot 1) + \frac{d}{d x} [4 \cos (6 x)]$

Step 3.3.9

Multiply $\sin (6 x)$ by $1$ .

$- 72 (x^{2} (- 6 \sin (6 x)) + \cos (6 x) (2 x)) - 48 (x (6 \cos (6 x)) + \sin (6 x)) + \frac{d}{d x} [4 \cos (6 x)]$

Step 3.4

Evaluate $\frac{d}{d x} [4 \cos (6 x)]$ .

Tap for more steps...

Step 3.4.1

Since $4$ is constant with respect to $x$ , the derivative of $4 \cos (6 x)$ with respect to $x$ is $4 \frac{d}{d x} [\cos (6 x)]$ .

$- 72 (x^{2} (- 6 \sin (6 x)) + \cos (6 x) (2 x)) - 48 (x (6 \cos (6 x)) + \sin (6 x)) + 4 \frac{d}{d x} [\cos (6 x)]$

Step 3.4.2

Differentiate using the chain rule, which states that $\frac{d}{d x} [f (g (x))]$ is $f' (g (x)) g' (x)$ where $f (x) = \cos (x)$ and $g (x) = 6 x$ .

Tap for more steps...

Step 3.4.2.1

To apply the Chain Rule, set $u_{3}$ as $6 x$ .

$- 72 (x^{2} (- 6 \sin (6 x)) + \cos (6 x) (2 x)) - 48 (x (6 \cos (6 x)) + \sin (6 x)) + 4 (\frac{d}{d u_{3}} [\cos (u_{3})] \frac{d}{d x} [6 x])$

Step 3.4.2.2

The derivative of $\cos (u_{3})$ with respect to $u_{3}$ is $- \sin (u_{3})$ .

$- 72 (x^{2} (- 6 \sin (6 x)) + \cos (6 x) (2 x)) - 48 (x (6 \cos (6 x)) + \sin (6 x)) + 4 (- \sin (u_{3}) \frac{d}{d x} [6 x])$

Step 3.4.2.3

Replace all occurrences of $u_{3}$ with $6 x$ .

$- 72 (x^{2} (- 6 \sin (6 x)) + \cos (6 x) (2 x)) - 48 (x (6 \cos (6 x)) + \sin (6 x)) + 4 (- \sin (6 x) \frac{d}{d x} [6 x])$

Step 3.4.3

Since $6$ is constant with respect to $x$ , the derivative of $6 x$ with respect to $x$ is $6 \frac{d}{d x} [x]$ .

$- 72 (x^{2} (- 6 \sin (6 x)) + \cos (6 x) (2 x)) - 48 (x (6 \cos (6 x)) + \sin (6 x)) + 4 (- \sin (6 x) (6 \frac{d}{d x} [x]))$

Step 3.4.4

Differentiate using the Power Rule which states that $\frac{d}{d x} [x^{n}]$ is $n x^{n - 1}$ where $n = 1$ .

$- 72 (x^{2} (- 6 \sin (6 x)) + \cos (6 x) (2 x)) - 48 (x (6 \cos (6 x)) + \sin (6 x)) + 4 (- \sin (6 x) (6 \cdot 1))$

Step 3.4.5

Multiply $6$ by $1$ .

$- 72 (x^{2} (- 6 \sin (6 x)) + \cos (6 x) (2 x)) - 48 (x (6 \cos (6 x)) + \sin (6 x)) + 4 (- \sin (6 x) \cdot 6)$

Step 3.4.6

Multiply $6$ by $- 1$ .

$- 72 (x^{2} (- 6 \sin (6 x)) + \cos (6 x) (2 x)) - 48 (x (6 \cos (6 x)) + \sin (6 x)) + 4 (- 6 \sin (6 x))$

Step 3.4.7

Multiply $- 6$ by $4$ .

$- 72 (x^{2} (- 6 \sin (6 x)) + \cos (6 x) (2 x)) - 48 (x (6 \cos (6 x)) + \sin (6 x)) - 24 \sin (6 x)$

Step 3.5

Simplify.

Tap for more steps...

Step 3.5.1

Apply the distributive property.

$- 72 (x^{2} (- 6 \sin (6 x))) - 72 (\cos (6 x) (2 x)) - 48 (x (6 \cos (6 x)) + \sin (6 x)) - 24 \sin (6 x)$

Step 3.5.2

Apply the distributive property.

$- 72 (x^{2} (- 6 \sin (6 x))) - 72 (\cos (6 x) (2 x)) - 48 (x (6 \cos (6 x))) - 48 \sin (6 x) - 24 \sin (6 x)$

Step 3.5.3

Combine terms.

Tap for more steps...

Step 3.5.3.1

Multiply $- 6$ by $- 72$ .

$432 (x^{2} (\sin (6 x))) - 72 (\cos (6 x) (2 x)) - 48 (x (6 \cos (6 x))) - 48 \sin (6 x) - 24 \sin (6 x)$

Step 3.5.3.2

Multiply $2$ by $- 72$ .

$432 x^{2} \sin (6 x) - 144 (\cos (6 x) (x)) - 48 (x (6 \cos (6 x))) - 48 \sin (6 x) - 24 \sin (6 x)$

Step 3.5.3.3

Multiply $6$ by $- 48$ .

$432 x^{2} \sin (6 x) - 144 \cos (6 x) x - 288 (x (\cos (6 x))) - 48 \sin (6 x) - 24 \sin (6 x)$

Step 3.5.3.4

Subtract $288 x \cos (6 x)$ from $- 144 \cos (6 x) x$ .

Tap for more steps...

Step 3.5.3.4.1

Move $\cos (6 x)$ .

$432 x^{2} \sin (6 x) - 144 x \cos (6 x) - 288 x \cos (6 x) - 48 \sin (6 x) - 24 \sin (6 x)$

Step 3.5.3.4.2

Subtract $288 x \cos (6 x)$ from $- 144 x \cos (6 x)$ .

$432 x^{2} \sin (6 x) - 432 x \cos (6 x) - 48 \sin (6 x) - 24 \sin (6 x)$

Step 3.5.3.5

Subtract $24 \sin (6 x)$ from $- 48 \sin (6 x)$ .

$f''' (x) = 432 x^{2} \sin (6 x) - 432 x \cos (6 x) - 72 \sin (6 x)$

Step 4

Find the fourth derivative.

Tap for more steps...

Step 4.1

By the Sum Rule, the derivative of $432 x^{2} \sin (6 x) - 432 x \cos (6 x) - 72 \sin (6 x)$ with respect to $x$ is $\frac{d}{d x} [432 x^{2} \sin (6 x)] + \frac{d}{d x} [- 432 x \cos (6 x)] + \frac{d}{d x} [- 72 \sin (6 x)]$ .

$\frac{d}{d x} [432 x^{2} \sin (6 x)] + \frac{d}{d x} [- 432 x \cos (6 x)] + \frac{d}{d x} [- 72 \sin (6 x)]$

Step 4.2

Evaluate $\frac{d}{d x} [432 x^{2} \sin (6 x)]$ .

Tap for more steps...

Step 4.2.1

Since $432$ is constant with respect to $x$ , the derivative of $432 x^{2} \sin (6 x)$ with respect to $x$ is $432 \frac{d}{d x} [x^{2} \sin (6 x)]$ .

$432 \frac{d}{d x} [x^{2} \sin (6 x)] + \frac{d}{d x} [- 432 x \cos (6 x)] + \frac{d}{d x} [- 72 \sin (6 x)]$

Step 4.2.2

Differentiate using the Product Rule which states that $\frac{d}{d x} [f (x) g (x)]$ is $f (x) \frac{d}{d x} [g (x)] + g (x) \frac{d}{d x} [f (x)]$ where $f (x) = x^{2}$ and $g (x) = \sin (6 x)$ .

$432 (x^{2} \frac{d}{d x} [\sin (6 x)] + \sin (6 x) \frac{d}{d x} [x^{2}]) + \frac{d}{d x} [- 432 x \cos (6 x)] + \frac{d}{d x} [- 72 \sin (6 x)]$

Step 4.2.3

Differentiate using the chain rule, which states that $\frac{d}{d x} [f (g (x))]$ is $f' (g (x)) g' (x)$ where $f (x) = \sin (x)$ and $g (x) = 6 x$ .

Tap for more steps...

Step 4.2.3.1

To apply the Chain Rule, set $u_{1}$ as $6 x$ .

$432 (x^{2} (\frac{d}{d u_{1}} [\sin (u_{1})] \frac{d}{d x} [6 x]) + \sin (6 x) \frac{d}{d x} [x^{2}]) + \frac{d}{d x} [- 432 x \cos (6 x)] + \frac{d}{d x} [- 72 \sin (6 x)]$

Step 4.2.3.2

The derivative of $\sin (u_{1})$ with respect to $u_{1}$ is $\cos (u_{1})$ .

$432 (x^{2} (\cos (u_{1}) \frac{d}{d x} [6 x]) + \sin (6 x) \frac{d}{d x} [x^{2}]) + \frac{d}{d x} [- 432 x \cos (6 x)] + \frac{d}{d x} [- 72 \sin (6 x)]$

Step 4.2.3.3

Replace all occurrences of $u_{1}$ with $6 x$ .

$432 (x^{2} (\cos (6 x) \frac{d}{d x} [6 x]) + \sin (6 x) \frac{d}{d x} [x^{2}]) + \frac{d}{d x} [- 432 x \cos (6 x)] + \frac{d}{d x} [- 72 \sin (6 x)]$

Step 4.2.4

Since $6$ is constant with respect to $x$ , the derivative of $6 x$ with respect to $x$ is $6 \frac{d}{d x} [x]$ .

$432 (x^{2} (\cos (6 x) (6 \frac{d}{d x} [x])) + \sin (6 x) \frac{d}{d x} [x^{2}]) + \frac{d}{d x} [- 432 x \cos (6 x)] + \frac{d}{d x} [- 72 \sin (6 x)]$

Step 4.2.5

Differentiate using the Power Rule which states that $\frac{d}{d x} [x^{n}]$ is $n x^{n - 1}$ where $n = 1$ .

$432 (x^{2} (\cos (6 x) (6 \cdot 1)) + \sin (6 x) \frac{d}{d x} [x^{2}]) + \frac{d}{d x} [- 432 x \cos (6 x)] + \frac{d}{d x} [- 72 \sin (6 x)]$

Step 4.2.6

Differentiate using the Power Rule which states that $\frac{d}{d x} [x^{n}]$ is $n x^{n - 1}$ where $n = 2$ .

$432 (x^{2} (\cos (6 x) (6 \cdot 1)) + \sin (6 x) (2 x)) + \frac{d}{d x} [- 432 x \cos (6 x)] + \frac{d}{d x} [- 72 \sin (6 x)]$

Step 4.2.7

Multiply $6$ by $1$ .

$432 (x^{2} (\cos (6 x) \cdot 6) + \sin (6 x) (2 x)) + \frac{d}{d x} [- 432 x \cos (6 x)] + \frac{d}{d x} [- 72 \sin (6 x)]$

Step 4.2.8

Move $6$ to the left of $\cos (6 x)$ .

$432 (x^{2} (6 \cos (6 x)) + \sin (6 x) (2 x)) + \frac{d}{d x} [- 432 x \cos (6 x)] + \frac{d}{d x} [- 72 \sin (6 x)]$

Step 4.3

Evaluate $\frac{d}{d x} [- 432 x \cos (6 x)]$ .

Tap for more steps...

Step 4.3.1

Since $- 432$ is constant with respect to $x$ , the derivative of $- 432 x \cos (6 x)$ with respect to $x$ is $- 432 \frac{d}{d x} [x \cos (6 x)]$ .

$432 (x^{2} (6 \cos (6 x)) + \sin (6 x) (2 x)) - 432 \frac{d}{d x} [x \cos (6 x)] + \frac{d}{d x} [- 72 \sin (6 x)]$

Step 4.3.2

Differentiate using the Product Rule which states that $\frac{d}{d x} [f (x) g (x)]$ is $f (x) \frac{d}{d x} [g (x)] + g (x) \frac{d}{d x} [f (x)]$ where $f (x) = x$ and $g (x) = \cos (6 x)$ .

$432 (x^{2} (6 \cos (6 x)) + \sin (6 x) (2 x)) - 432 (x \frac{d}{d x} [\cos (6 x)] + \cos (6 x) \frac{d}{d x} [x]) + \frac{d}{d x} [- 72 \sin (6 x)]$

Step 4.3.3

Differentiate using the chain rule, which states that $\frac{d}{d x} [f (g (x))]$ is $f' (g (x)) g' (x)$ where $f (x) = \cos (x)$ and $g (x) = 6 x$ .

Tap for more steps...

Step 4.3.3.1

To apply the Chain Rule, set $u_{2}$ as $6 x$ .

$432 (x^{2} (6 \cos (6 x)) + \sin (6 x) (2 x)) - 432 (x (\frac{d}{d u_{2}} [\cos (u_{2})] \frac{d}{d x} [6 x]) + \cos (6 x) \frac{d}{d x} [x]) + \frac{d}{d x} [- 72 \sin (6 x)]$

Step 4.3.3.2

The derivative of $\cos (u_{2})$ with respect to $u_{2}$ is $- \sin (u_{2})$ .

$432 (x^{2} (6 \cos (6 x)) + \sin (6 x) (2 x)) - 432 (x (- \sin (u_{2}) \frac{d}{d x} [6 x]) + \cos (6 x) \frac{d}{d x} [x]) + \frac{d}{d x} [- 72 \sin (6 x)]$

Step 4.3.3.3

Replace all occurrences of $u_{2}$ with $6 x$ .

$432 (x^{2} (6 \cos (6 x)) + \sin (6 x) (2 x)) - 432 (x (- \sin (6 x) \frac{d}{d x} [6 x]) + \cos (6 x) \frac{d}{d x} [x]) + \frac{d}{d x} [- 72 \sin (6 x)]$

Step 4.3.4

Since $6$ is constant with respect to $x$ , the derivative of $6 x$ with respect to $x$ is $6 \frac{d}{d x} [x]$ .

$432 (x^{2} (6 \cos (6 x)) + \sin (6 x) (2 x)) - 432 (x (- \sin (6 x) (6 \frac{d}{d x} [x])) + \cos (6 x) \frac{d}{d x} [x]) + \frac{d}{d x} [- 72 \sin (6 x)]$

Step 4.3.5

Differentiate using the Power Rule which states that $\frac{d}{d x} [x^{n}]$ is $n x^{n - 1}$ where $n = 1$ .

$432 (x^{2} (6 \cos (6 x)) + \sin (6 x) (2 x)) - 432 (x (- \sin (6 x) (6 \cdot 1)) + \cos (6 x) \frac{d}{d x} [x]) + \frac{d}{d x} [- 72 \sin (6 x)]$

Step 4.3.6

Differentiate using the Power Rule which states that $\frac{d}{d x} [x^{n}]$ is $n x^{n - 1}$ where $n = 1$ .

$432 (x^{2} (6 \cos (6 x)) + \sin (6 x) (2 x)) - 432 (x (- \sin (6 x) (6 \cdot 1)) + \cos (6 x) \cdot 1) + \frac{d}{d x} [- 72 \sin (6 x)]$

Step 4.3.7

Multiply $6$ by $1$ .

$432 (x^{2} (6 \cos (6 x)) + \sin (6 x) (2 x)) - 432 (x (- \sin (6 x) \cdot 6) + \cos (6 x) \cdot 1) + \frac{d}{d x} [- 72 \sin (6 x)]$

Step 4.3.8

Multiply $6$ by $- 1$ .

$432 (x^{2} (6 \cos (6 x)) + \sin (6 x) (2 x)) - 432 (x (- 6 \sin (6 x)) + \cos (6 x) \cdot 1) + \frac{d}{d x} [- 72 \sin (6 x)]$

Step 4.3.9

Multiply $\cos (6 x)$ by $1$ .

$432 (x^{2} (6 \cos (6 x)) + \sin (6 x) (2 x)) - 432 (x (- 6 \sin (6 x)) + \cos (6 x)) + \frac{d}{d x} [- 72 \sin (6 x)]$

Step 4.4

Evaluate $\frac{d}{d x} [- 72 \sin (6 x)]$ .

Tap for more steps...

Step 4.4.1

Since $- 72$ is constant with respect to $x$ , the derivative of $- 72 \sin (6 x)$ with respect to $x$ is $- 72 \frac{d}{d x} [\sin (6 x)]$ .

$432 (x^{2} (6 \cos (6 x)) + \sin (6 x) (2 x)) - 432 (x (- 6 \sin (6 x)) + \cos (6 x)) - 72 \frac{d}{d x} [\sin (6 x)]$

Step 4.4.2

Differentiate using the chain rule, which states that $\frac{d}{d x} [f (g (x))]$ is $f' (g (x)) g' (x)$ where $f (x) = \sin (x)$ and $g (x) = 6 x$ .

Tap for more steps...

Step 4.4.2.1

To apply the Chain Rule, set $u_{3}$ as $6 x$ .

$432 (x^{2} (6 \cos (6 x)) + \sin (6 x) (2 x)) - 432 (x (- 6 \sin (6 x)) + \cos (6 x)) - 72 (\frac{d}{d u_{3}} [\sin (u_{3})] \frac{d}{d x} [6 x])$

Step 4.4.2.2

The derivative of $\sin (u_{3})$ with respect to $u_{3}$ is $\cos (u_{3})$ .

$432 (x^{2} (6 \cos (6 x)) + \sin (6 x) (2 x)) - 432 (x (- 6 \sin (6 x)) + \cos (6 x)) - 72 (\cos (u_{3}) \frac{d}{d x} [6 x])$

Step 4.4.2.3

Replace all occurrences of $u_{3}$ with $6 x$ .

$432 (x^{2} (6 \cos (6 x)) + \sin (6 x) (2 x)) - 432 (x (- 6 \sin (6 x)) + \cos (6 x)) - 72 (\cos (6 x) \frac{d}{d x} [6 x])$

Step 4.4.3

Since $6$ is constant with respect to $x$ , the derivative of $6 x$ with respect to $x$ is $6 \frac{d}{d x} [x]$ .

$432 (x^{2} (6 \cos (6 x)) + \sin (6 x) (2 x)) - 432 (x (- 6 \sin (6 x)) + \cos (6 x)) - 72 (\cos (6 x) (6 \frac{d}{d x} [x]))$

Step 4.4.4

Differentiate using the Power Rule which states that $\frac{d}{d x} [x^{n}]$ is $n x^{n - 1}$ where $n = 1$ .

$432 (x^{2} (6 \cos (6 x)) + \sin (6 x) (2 x)) - 432 (x (- 6 \sin (6 x)) + \cos (6 x)) - 72 (\cos (6 x) (6 \cdot 1))$

Step 4.4.5

Multiply $6$ by $1$ .

$432 (x^{2} (6 \cos (6 x)) + \sin (6 x) (2 x)) - 432 (x (- 6 \sin (6 x)) + \cos (6 x)) - 72 (\cos (6 x) \cdot 6)$

Step 4.4.6

Move $6$ to the left of $\cos (6 x)$ .

$432 (x^{2} (6 \cos (6 x)) + \sin (6 x) (2 x)) - 432 (x (- 6 \sin (6 x)) + \cos (6 x)) - 72 (6 \cdot \cos (6 x))$

Step 4.4.7

Multiply $6$ by $- 72$ .

$432 (x^{2} (6 \cos (6 x)) + \sin (6 x) (2 x)) - 432 (x (- 6 \sin (6 x)) + \cos (6 x)) - 432 \cos (6 x)$

Step 4.5

Simplify.

Tap for more steps...

Step 4.5.1

Apply the distributive property.

$432 (x^{2} (6 \cos (6 x))) + 432 (\sin (6 x) (2 x)) - 432 (x (- 6 \sin (6 x)) + \cos (6 x)) - 432 \cos (6 x)$

Step 4.5.2

Apply the distributive property.

$432 (x^{2} (6 \cos (6 x))) + 432 (\sin (6 x) (2 x)) - 432 (x (- 6 \sin (6 x))) - 432 \cos (6 x) - 432 \cos (6 x)$

Step 4.5.3

Combine terms.

Tap for more steps...

Step 4.5.3.1

Multiply $6$ by $432$ .

$2592 (x^{2} (\cos (6 x))) + 432 (\sin (6 x) (2 x)) - 432 (x (- 6 \sin (6 x))) - 432 \cos (6 x) - 432 \cos (6 x)$

Step 4.5.3.2

Multiply $2$ by $432$ .

$2592 x^{2} \cos (6 x) + 864 (\sin (6 x) (x)) - 432 (x (- 6 \sin (6 x))) - 432 \cos (6 x) - 432 \cos (6 x)$

Step 4.5.3.3

Multiply $- 6$ by $- 432$ .

$2592 x^{2} \cos (6 x) + 864 \sin (6 x) x + 2592 (x (\sin (6 x))) - 432 \cos (6 x) - 432 \cos (6 x)$

Step 4.5.3.4

Add $864 \sin (6 x) x$ and $2592 x \sin (6 x)$ .

Tap for more steps...

Step 4.5.3.4.1

Move $\sin (6 x)$ .

$2592 x^{2} \cos (6 x) + 864 x \sin (6 x) + 2592 x \sin (6 x) - 432 \cos (6 x) - 432 \cos (6 x)$

Step 4.5.3.4.2

Add $864 x \sin (6 x)$ and $2592 x \sin (6 x)$ .

$2592 x^{2} \cos (6 x) + 3456 x \sin (6 x) - 432 \cos (6 x) - 432 \cos (6 x)$

Step 4.5.3.5

Subtract $432 \cos (6 x)$ from $- 432 \cos (6 x)$ .

$f^{4} (x) = 2592 x^{2} \cos (6 x) + 3456 x \sin (6 x) - 864 \cos (6 x)$

Step 5

The fourth derivative of $f (x)$ with respect to $x$ is $2592 x^{2} \cos (6 x) + 3456 x \sin (6 x) - 864 \cos (6 x)$ .

$2592 x^{2} \cos (6 x) + 3456 x \sin (6 x) - 864 \cos (6 x)$