Question #8842f

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Answer 1 · 2017-09-23T17:28:37

All you need to do is plug $5$ $5$ into the derivative.

$f'(x)=-sinx-4sec^2x$

$f'(5)=-sin(5)-4sec^2(5)$

You can plug this straight into something like Wolfram Alpha.

On a calculator, depending on what type you have, you may not have the $sec$ button and instead have to use $cos$ :

$f'(5)=-sin(5)-4/(cos(5))^2$

I also assume you're working with radians. Without knowing how many digits you need, you should get:

$f'(5)=-48.75260255517...$