Question

Find the exact value by using a half-angle identity.

cosine of negative pi divided by eight

Answer 1

sorry i dont understand what you mean by that could you please reiterate @SolomonZelman

Answer 2

` π = 1 8 0 º `

Answer 3

Then divide 180 by -8, so you get -22.5
And that is equivalent to (1/2) × 45

Answer 4

yes i understand that if you could how does that contribute to the problem @SolomonZelman

Answer 5

is that using the half angle identity though? @SolomonZelman

Answer 6

if possible could anyone come and help me through this @ParthKohli @jim_thompson5910

Answer 7

From Mathematica 9 Home Edition:\[\text{ToRadicals}\left[\cos \left(-\frac{\pi }{8}\right)\right]=\frac{\sqrt{2+\sqrt{2}}}{2} \]

Answer 8

thank you for the answer but could you help me go through the problem if you could

Answer 9

@robtobey