Question

Use the cosine sum and difference identities to find the exact value.

COS(5pi/12)

Answer 1

Square root of 2(square root of 3-1)/4. Honestly apex is trying to mess you up lol

Answer 2

5π/12 = (5 · 180°) : 12 = 75°
cos 75° = cos ( 45° + 30° )= cos 45° cos 30° - sin 45° sin 30° =
=√2/2 * √3/2 - √2/2 * 1/2 =
`( √(6) )/(4) - ( √(2) )/(4)= ( √(6) - √(2) )/(4)`
=(2.4495 - 1.4142): 4 = 0.258825