Question

Evaluate: cos(Arctan 15/8)

Answer 1

tan = sin/cos. sin(arctan15/8)/cos(arctan15/8) = 15/8 and sin^2(arctan15/8) + cos^2(arctan15/8) =1. So you have two equations. try to solve them)

Answer 2

i appreciate the help but i still cannot figure this out.

Answer 3

hey you still there?

Answer 4

let's arctan15/8 = a. We have sin(a) = 15/8cos(a) and cos^2(a) = sin^2(a). Then cos^2(a) = 1 - 225/64cos^2(a). So cos^2(a) = 1/(1 - 225/64) or \[\cos(a) = \sqrt{1/(1 + 225/64 )}\]

Answer 5

i kept writing 18 for some reason so ignore the scratch outs

Answer 6

you can draw a right traingle they are pretty easy to work with and label the sides based on what you have up there

Answer 7

alright now it makes sense, thanks a lot guys