Calculus Examples

$y = \frac{\cos (t^{4})}{\tan (4 t)}$

Step 1

Rewrite $\tan (4 t)$ in terms of sines and cosines.

$\frac{d}{d t} [\frac{\cos (t^{4})}{\frac{\sin (4 t)}{\cos (4 t)}}]$

Step 2

Multiply by the reciprocal of the fraction to divide by $\frac{\sin (4 t)}{\cos (4 t)}$ .

$\frac{d}{d t} [\frac{\cos (t^{4}) \cos (4 t)}{\sin (4 t)}]$

Step 3

Convert from $\frac{\cos (t^{4}) \cos (4 t)}{\sin (4 t)}$ to $\cos (t^{4}) \cot (4 t)$ .

$\frac{d}{d t} [\cos (t^{4}) \cot (4 t)]$

Step 4

Differentiate using the Product Rule which states that $\frac{d}{d t} [f (t) g (t)]$ is $f (t) \frac{d}{d t} [g (t)] + g (t) \frac{d}{d t} [f (t)]$ where $f (t) = \cos (t^{4})$ and $g (t) = \cot (4 t)$ .

$\cos (t^{4}) \frac{d}{d t} [\cot (4 t)] + \cot (4 t) \frac{d}{d t} [\cos (t^{4})]$

Step 5

Differentiate using the chain rule, which states that $\frac{d}{d t} [f (g (t))]$ is $f' (g (t)) g' (t)$ where $f (t) = \cot (t)$ and $g (t) = 4 t$ .

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Step 5.1

To apply the Chain Rule, set $u_{1}$ as $4 t$ .

$\cos (t^{4}) (\frac{d}{d u_{1}} [\cot (u_{1})] \frac{d}{d t} [4 t]) + \cot (4 t) \frac{d}{d t} [\cos (t^{4})]$

Step 5.2

The derivative of $\cot (u_{1})$ with respect to $u_{1}$ is $- \csc^{2} (u_{1})$ .

$\cos (t^{4}) (- \csc^{2} (u_{1}) \frac{d}{d t} [4 t]) + \cot (4 t) \frac{d}{d t} [\cos (t^{4})]$

Step 5.3

Replace all occurrences of $u_{1}$ with $4 t$ .

$\cos (t^{4}) (- \csc^{2} (4 t) \frac{d}{d t} [4 t]) + \cot (4 t) \frac{d}{d t} [\cos (t^{4})]$

Step 6

Differentiate.

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Step 6.1

Since $4$ is constant with respect to $t$ , the derivative of $4 t$ with respect to $t$ is $4 \frac{d}{d t} [t]$ .

$\cos (t^{4}) (- \csc^{2} (4 t) (4 \frac{d}{d t} [t])) + \cot (4 t) \frac{d}{d t} [\cos (t^{4})]$

Step 6.2

Multiply $4$ by $- 1$ .

$\cos (t^{4}) (- 4 \csc^{2} (4 t) \frac{d}{d t} [t]) + \cot (4 t) \frac{d}{d t} [\cos (t^{4})]$

Step 6.3

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

$\cos (t^{4}) (- 4 \csc^{2} (4 t) \cdot 1) + \cot (4 t) \frac{d}{d t} [\cos (t^{4})]$

Step 6.4

Multiply $- 4$ by $1$ .

$\cos (t^{4}) (- 4 \csc^{2} (4 t)) + \cot (4 t) \frac{d}{d t} [\cos (t^{4})]$

Step 7

Differentiate using the chain rule, which states that $\frac{d}{d t} [f (g (t))]$ is $f' (g (t)) g' (t)$ where $f (t) = \cos (t)$ and $g (t) = t^{4}$ .

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Step 7.1

To apply the Chain Rule, set $u_{2}$ as $t^{4}$ .

$\cos (t^{4}) (- 4 \csc^{2} (4 t)) + \cot (4 t) (\frac{d}{d u_{2}} [\cos (u_{2})] \frac{d}{d t} [t^{4}])$

Step 7.2

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

$\cos (t^{4}) (- 4 \csc^{2} (4 t)) + \cot (4 t) (- \sin (u_{2}) \frac{d}{d t} [t^{4}])$

Step 7.3

Replace all occurrences of $u_{2}$ with $t^{4}$ .

$\cos (t^{4}) (- 4 \csc^{2} (4 t)) + \cot (4 t) (- \sin (t^{4}) \frac{d}{d t} [t^{4}])$

Step 8

Differentiate using the Power Rule.

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Step 8.1

Differentiate using the Power Rule which states that $\frac{d}{d t} [t^{n}]$ is $n t^{n - 1}$ where $n = 4$ .

$\cos (t^{4}) (- 4 \csc^{2} (4 t)) + \cot (4 t) (- \sin (t^{4}) (4 t^{3}))$

Step 8.2

Simplify the expression.

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Step 8.2.1

Multiply $4$ by $- 1$ .

$\cos (t^{4}) (- 4 \csc^{2} (4 t)) + \cot (4 t) (- 4 \sin (t^{4}) t^{3})$

Step 8.2.2

Reorder terms.

$- 4 \csc^{2} (4 t) \cos (t^{4}) - 4 t^{3} \cot (4 t) \sin (t^{4})$