Question

Use the appropriate sum or difference identity to find the exact value of cos (7pi/12)

Answer 1

cos(7pi/12) = cos(3pi/12+4pi/12)
= cos (pi/4 + pi/3)
= cos pi/4 * cos pi/3 - sin pi/4 * sin pi/3
go ahead.. put values and get answer :)

Answer 2

ive got (sqrt2 +sqrt6)/4 is that right