Question

f '(pi/4) = cos(x) - xsin(x)

Answer 1

wow. does this mean
\[f'(x)=\cos(x)-x\sin(x)\] and you want
\[f'(\frac{\pi}{4})\]?

Answer 2

in other words you took the derivative of
\[f(x)=x\cos(x)\] and now you want to evaluate at
\[\frac{\pi}{4}\]

Answer 3

yes that's what i tried to say

Answer 4

yikes. asnwer is
\[\frac{\sqrt{2}}{2}-\frac{\pi}{4}\frac{\sqrt{2}}{2}\]

Answer 5

cos(pi/4)-(pi/4)sin(pi/4)
(sqrt(2)/2)-(pi/4)(sqrt(2)/2)

Answer 6

my computer takes forever to post an answer

Answer 7

its okay but thank you very much for helping me