Calculus Examples

$x - x^{2} \cos (x)$

Step 1

Differentiate.

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Step 1.1

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

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

Step 1.2

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

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

Step 2

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

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Step 2.1

Since $- 1$ is constant with respect to $x$ , the derivative of $- x^{2} \cos (x)$ with respect to $x$ is $- \frac{d}{d x} [x^{2} \cos (x)]$ .

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

Step 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 $g (x) = \cos (x)$ .

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

Step 2.3

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

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

Step 2.4

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

$1 - (x^{2} (- \sin (x)) + \cos (x) (2 x))$

Step 3

Simplify.

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Step 3.1

Apply the distributive property.

$1 - (x^{2} (- \sin (x))) - (\cos (x) (2 x))$

Step 3.2

Combine terms.

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Step 3.2.1

Multiply $- 1$ by $- 1$ .

$1 + 1 (x^{2} (\sin (x))) - (\cos (x) (2 x))$

Step 3.2.2

Multiply $x^{2}$ by $1$ .

$1 + x^{2} \sin (x) - (\cos (x) (2 x))$

Step 3.2.3

Multiply $2$ by $- 1$ .

$1 + x^{2} \sin (x) - 2 \cos (x) x$

Step 3.3

Reorder terms.

$x^{2} \sin (x) - 2 x \cos (x) + 1$