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Section 3.9 : Chain Rule

26. Differentiate \(h\left( z \right) = {\tan ^4}\left( {{z^2} + 1} \right)\) .

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Hint : Sometimes the Chain Rule will need to be done multiple times before we finish taking the derivative.
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This problem will require multiple uses of the Chain Rule and so we’ll step though the derivative process to make each use clear. Also, recall that,

\[{\tan ^4}\left( x \right) = {\left[ {\tan \left( x \right)} \right]^4}\]

Here is the first step of the derivative and we’ll need to use the Chain Rule in this step.

\[h'\left( z \right) = 4{\tan ^3}\left( {{z^2} + 1} \right)\frac{d}{{dz}}\left[ {\tan \left( {{z^2} + 1} \right)} \right]\] Show Step 2

As we can see the derivative from the previous step will also require the Chain Rule.

The derivative is then,

\[h'\left( z \right) = 4{\tan ^3}\left( {{z^2} + 1} \right){\sec ^2}\left( {{z^2} + 1} \right)\left( {2z} \right) = \require{bbox} \bbox[2pt,border:1px solid black]{{8z{{\tan }^3}\left( {{z^2} + 1} \right){{\sec }^2}\left( {{z^2} + 1} \right)}}\]