Question

вычислите (1-cos a)(1+cos a) / 2sin a, если sin a= -2/3

Answer 1

1-cos^2a/2 sin a=sin^2 a/ 2 sin a=sin a/2=-2/3/2=-1/3

Answer 2

1-cos^2a/2sina=sin^2a/2sina=sina/2=-2/3/2=-1/3