Question

Use a double or half angle identity to find cos (7π/12). Provide the exact answer in simplest form (no approximations)

Answer 1

$(\sqrt{6} + \sqrt{2})/4$. cos($7 \pi /12$) is the same thing as cos(π/3 + π/4) and then you use the formula cos(a + b) = cos(a)cos(b) + sin(a)sin(b)