1. Find the exact value of the expression.

Question

cos pi/16 * cos 3pi/16 - sin pi/16 * sin 3pi/16

My ans: sqrt2/2

2. Find the exact value of the sin of the angle.
17pi/12 = 7pi/6 + pi/4

My ans: (sqrt2 - sqrt6)/4

Answer 1

Hmmm. I get

-(√2+√6)/4

Better check your +- signs.