Question

упростите выражение cos(pi/6+a)-^3/2cosa

Answer 1

$cos(\frac{\pi}{6}+a)-\frac{\sqrt3}{2}cosa = cos\frac{\pi}{6}cosa-sin\frac{\pi}{6}sina-\frac{\sqrt3}{2}cosa=\\ \frac{\sqrt3}{2}cosa-\frac{1}{2}sina-\frac{\sqrt3}{2}cosa=-\frac{1}{2}sina$