Question

If f(x)= cos^2x, then f''(pi) =

Answer 1

f'(x) = 2*cos(x) * - sin(x), right?

Answer 2

i would write it as
f'(x) = 2*cos(x) * [- sin(x)]
to avoid confusion, but yeah

Answer 3

\[f''(x)=(-2\sin(x))(-\sin(x))+(-\cos(x))(2\cos(x))\]

Answer 4

looking good

Answer 5

yes:)

Answer 6

\[2\sin^2(x) + [-2\cos^2(x)]\]

Answer 7

so far so good

Answer 8

you can rewirte it is a double angle rule, after factoring out a 2

Answer 9

factor out of \(\large\color{bla k}{ 2 }\), and use: \(\large\color{ k}{ \cos^2(s)-\sin^2(s) =\cos(2s) }\)

Answer 10

so 2(-cos(2x))

Answer 11

yes, and plug in pi

Answer 12

I get -1.987986 but my options are -2, 0, 1, 2, and 2pi

Answer 13

I guess I'll just round it to -2 :)

Answer 14

yep

Answer 15

cos(2pi) is an exact number

Answer 16

Which grade math is it

Answer 17

yes it is:D exact num

Answer 18

OOh lol the unit circle, yep, maybe I should stay away from calculators lel.

Answer 19

I forgot it was an exact number. D:

Answer 20

yeah, or if you use them at least remember to make sure you are in radian mode when using pi

Answer 21

Thank you :)

Answer 22

welcome!

Answer 23

which grade math is it

Answer 24

Calculus I

Answer 25

ok

Answer 26

Is it hard

Answer 27

I have same math next semister