# help in differentiating

• Mar 13th 2010, 04:50 AM
goaway716
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)
• Mar 13th 2010, 05:56 AM
skeeter
Quote:

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) ...
• Mar 13th 2010, 06:25 AM
goaway716
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
• Mar 13th 2010, 06:34 AM
e^(i*pi)
Your $f'(x)$ looks fine to me

You can use the quotient rule on the second term.

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

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