Question

Найдите значение cos(a-60),если sin a=1/3 и 90

Answer 1

cosa=-√(1-sina)=-√(1-1/9)=-√(8/9)=-2√2/3
cos(a-60)=cosa*cos60+sina*sin60=-2√2/3*1/2+1/3*√3/2=(-2√2+√3)/6