Question

cos a = -4:5 э(3,14 :2 и 3,14)
найти sin2a , cos2a

Answer 1

sina=√1-cos²a=√1-16/25=3/5
sin2a=2sinacosa=2*3/5*(-4/5)=-24/25
cos2a=cos²a-sin²a=16/25-9/25=7/25