Calculus Examples

$3 x \arctan (5 x)$

Step 1

Since $3$ is constant with respect to $x$ , the derivative of $3 x \arctan (5 x)$ with respect to $x$ is $3 \frac{d}{d x} [x \arctan (5 x)]$ .

$3 \frac{d}{d x} [x \arctan (5 x)]$

Step 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 $g (x) = \arctan (5 x)$ .

$3 (x \frac{d}{d x} [\arctan (5 x)] + \arctan (5 x) \frac{d}{d x} [x])$

Step 3

Differentiate using the chain rule, which states that $\frac{d}{d x} [f (g (x))]$ is $f' (g (x)) g' (x)$ where $f (x) = \arctan (x)$ and $g (x) = 5 x$ .

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Step 3.1

To apply the Chain Rule, set $u$ as $5 x$ .

$3 (x (\frac{d}{d u} [\arctan (u)] \frac{d}{d x} [5 x]) + \arctan (5 x) \frac{d}{d x} [x])$

Step 3.2

The derivative of $\arctan (u)$ with respect to $u$ is $\frac{1}{1 + u^{2}}$ .

$3 (x (\frac{1}{1 + u^{2}} \frac{d}{d x} [5 x]) + \arctan (5 x) \frac{d}{d x} [x])$

Step 3.3

Replace all occurrences of $u$ with $5 x$ .

$3 (x (\frac{1}{1 + {(5 x)}^{2}} \frac{d}{d x} [5 x]) + \arctan (5 x) \frac{d}{d x} [x])$

Step 4

Differentiate.

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Step 4.1

Factor $5$ out of $5 x$ .

$3 (x (\frac{1}{1 + {(5 (x))}^{2}} \frac{d}{d x} [5 x]) + \arctan (5 x) \frac{d}{d x} [x])$

Step 4.2

Combine fractions.

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Step 4.2.1

Simplify the expression.

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Step 4.2.1.1

Apply the product rule to $5 (x)$ .

$3 (x (\frac{1}{1 + 5^{2} x^{2}} \frac{d}{d x} [5 x]) + \arctan (5 x) \frac{d}{d x} [x])$

Step 4.2.1.2

Raise $5$ to the power of $2$ .

$3 (x (\frac{1}{1 + 25 x^{2}} \frac{d}{d x} [5 x]) + \arctan (5 x) \frac{d}{d x} [x])$

Step 4.2.2

Combine $\frac{1}{1 + 25 x^{2}}$ and $x$ .

$3 (\frac{x}{1 + 25 x^{2}} \frac{d}{d x} [5 x] + \arctan (5 x) \frac{d}{d x} [x])$

Step 4.3

Since $5$ is constant with respect to $x$ , the derivative of $5 x$ with respect to $x$ is $5 \frac{d}{d x} [x]$ .

$3 (\frac{x}{1 + 25 x^{2}} (5 \frac{d}{d x} [x]) + \arctan (5 x) \frac{d}{d x} [x])$

Step 4.4

Combine $5$ and $\frac{x}{1 + 25 x^{2}}$ .

$3 (\frac{5 x}{1 + 25 x^{2}} \frac{d}{d x} [x] + \arctan (5 x) \frac{d}{d x} [x])$

Step 4.5

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

$3 (\frac{5 x}{1 + 25 x^{2}} \cdot 1 + \arctan (5 x) \frac{d}{d x} [x])$

Step 4.6

Multiply $\frac{5 x}{1 + 25 x^{2}}$ by $1$ .

$3 (\frac{5 x}{1 + 25 x^{2}} + \arctan (5 x) \frac{d}{d x} [x])$

Step 4.7

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

$3 (\frac{5 x}{1 + 25 x^{2}} + \arctan (5 x) \cdot 1)$

Step 4.8

Multiply $\arctan (5 x)$ by $1$ .

$3 (\frac{5 x}{1 + 25 x^{2}} + \arctan (5 x))$

Step 5

To write $\arctan (5 x)$ as a fraction with a common denominator, multiply by $\frac{1 + 25 x^{2}}{1 + 25 x^{2}}$ .

$3 (\frac{5 x}{1 + 25 x^{2}} + \frac{\arctan (5 x) (1 + 25 x^{2})}{1 + 25 x^{2}})$

Step 6

Combine the numerators over the common denominator.

$3 \frac{5 x + \arctan (5 x) (1 + 25 x^{2})}{1 + 25 x^{2}}$

Step 7

Combine $3$ and $\frac{5 x + \arctan (5 x) (1 + 25 x^{2})}{1 + 25 x^{2}}$ .

$\frac{3 (5 x + \arctan (5 x) (1 + 25 x^{2}))}{1 + 25 x^{2}}$

Step 8

Simplify.

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Step 8.1

Apply the distributive property.

$\frac{3 (5 x + \arctan (5 x) \cdot 1 + \arctan (5 x) (25 x^{2}))}{1 + 25 x^{2}}$

Step 8.2

Apply the distributive property.

$\frac{3 (5 x) + 3 (\arctan (5 x) \cdot 1) + 3 (\arctan (5 x) (25 x^{2}))}{1 + 25 x^{2}}$

Step 8.3

Simplify the numerator.

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Step 8.3.1

Simplify each term.

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Step 8.3.1.1

Multiply $5$ by $3$ .

$\frac{15 x + 3 (\arctan (5 x) \cdot 1) + 3 (\arctan (5 x) (25 x^{2}))}{1 + 25 x^{2}}$

Step 8.3.1.2

Multiply $\arctan (5 x)$ by $1$ .

$\frac{15 x + 3 \arctan (5 x) + 3 (\arctan (5 x) (25 x^{2}))}{1 + 25 x^{2}}$

Step 8.3.1.3

Rewrite using the commutative property of multiplication.

$\frac{15 x + 3 \arctan (5 x) + 3 (25 \arctan (5 x) x^{2})}{1 + 25 x^{2}}$

Step 8.3.1.4

Multiply $25$ by $3$ .

$\frac{15 x + 3 \arctan (5 x) + 75 \arctan (5 x) x^{2}}{1 + 25 x^{2}}$

Step 8.3.2

Reorder factors in $15 x + 3 \arctan (5 x) + 75 \arctan (5 x) x^{2}$ .

$\frac{15 x + 3 \arctan (5 x) + 75 x^{2} \arctan (5 x)}{1 + 25 x^{2}}$

Step 8.4

Reorder terms.

$\frac{75 x^{2} \arctan (5 x) + 15 x + 3 \arctan (5 x)}{25 x^{2} + 1}$