Question

Вычислите значение выражения 5cos(2arcsin1/3) - 2

Answer 1

arcsin(1/3) = arccos(sqrt(1-1/9)) = arccos(sqrt(8/9))=arccos[2*sqrt2 / 3]

5cos( arccos[2*sqrt2 / 3]) - 2 = 5* 2*sqrt2 / 3 - 2 = (10sqrt2 - 6)/3