Answer:
(√6 - √2) / 4
Step-by-step explanation:
cos(x+y) = cosx siny - sinx cosy
cos(75°) = cos(30°+45°) = cos30° sin45° -sin30°cos45°
= √3/2 * √2/2 - 1/2 * √2/2
=(√6 - √2) / 4
