# Thread: help in differentiating

1. ## help in differentiating

function f is defined by f(x)=4sin(x)+9/(1+sin(x)) with 0<=x<=pi

1)Evaluate the first and second derivative of f.
2)Find and classify the stationary points of the funtion
3)Find the greatest and least values of f(x)

2. Originally Posted by goaway716
function f is defined by f(x)=4sin(x)+9/(1+sin(x)) with 0<=x<=pi

1)Evaluate the first and second derivative of f.
2)Find and classify the stationary points of the funtion
3)Find the greatest and least values of f(x)
ok, start by letting us see what you got for f'(x) ...

3. ## got the first derivative

dy/dx=4cos(x)-9cos(x)/(1+sinx)^2

struggling with the second derivative for the first part of the question

4. Your $f'(x)$ looks fine to me

You can use the quotient rule on the second term.

$u = 9\cos(x) \: \rightarrow \: u' = -9\sin(x)$

$v = [1+sin(x)]^2 \: \: \rightarrow \: v' = 2\cos(x)[1+\sin(x)]$