Question

arccos(2cos^2(3pi/8)-1)

Answer 1

First find out value of 2cos^2(3pi/8) = ----? can you try ?

Answer 2

I have tried but I've been unsuccessful, I'm meant to evaluate without the use of a calculator

Answer 3

use cos^2(x) = (1/2) (cos(2x) +1)

Answer 4

Yes, I've already done so, but i'm stuck after that

Answer 5

what did you get afterward?

Answer 6

Nothing, I'm utterly confounded after this step

Answer 7

did you have arccos(cos(3pi/4)) ?

Answer 8

since 0<= 3pi/4 <= pi, 3pi/4 is your final answer

Answer 9

how did you get arccos(cos(3pi/4))?

Answer 10

using the formula above I gave you

Answer 11

cos^2(3pi/8) = (1/2) (cos(2 * 3pi/8) + 1)