Question

I really need help. (see attachment)

Answer 1

ok, you are given:\[f(x)=\cos(x)\]and have been asked to find:\[f'(\frac{\pi}{2})\]
so first work out what f'(x) is.

Answer 2

f'(x) represents the derivative of f(x) with respect to x.

Answer 3

it's sin x right?

Answer 4

-sinx

Answer 5

correct

Answer 6

then plug it in.

Answer 7

its 1. right?

Answer 8

so now you just need to work out the value of -sin(x) when x=\(\frac{\pi}{2}\)

Answer 9

remember its "-sin(x)" not "sin(x)"

Answer 10

oh yea.....-1

Answer 11

perfect! - well done!

Answer 12

thanks.

Answer 13

yw