Question

Упростите:
$cos2α+2sin(α+30°)sin(α-30°)$

Answer 1

сos2a+cos(a+30-a+30)-cos(a+30+a-30)=cos2a+cos60-cos2a=1/2

Answer 2

$cos2a+2sin(a+30)sin(a-30)=cos2a+2cdot0.5(cos(a+30-a+30)-cos(a+30+a-30))=cos2a+cos60-cos2a=cos60=0.5$