Question

Cos квадрат 150 - sin квадрат120

Answer 1

$cos^2150-sin^2120=cos^230-sin^260=(\sqrt{2}/2)^2- (\sqrt{2}/2)^2=0$

Answer 2

cos^2 (150) - sin^2 (120) = cos^2 (90+60) - sin^2 (180-60) = (НЕ КОСИНУС, А СИНУС) sin^ 2 (60) - sin^2 (60) = 0