Cos2a,если cosa=3/5 и 0

Question

Cos2a,если cosa=3/5 и 0

Answer 1

Cos2a = cos^2a-sin^2a = cos^2a - (1-cos^2a) = 2cos^2a -1
1) cosa = 3/5
2*(3/5)^2 -1 = 7/25
2) cosa =0
2*0-1 = -1