Question

cosх + cos(π-х) + sin(π/2-х) = sinπ/2

Answer 1

cosx+cosx+cosx=1

3cosx=sin^2x+cos^2x
(сокращаем cosx и ^2)=
2cosx=sin^2x+cosx
2cosx-cosx=sin^2x
cosx=sin^2x