Question

Корень из 1-1/5 cos x равен sin x

Answer 1

√(1-(1/5) ·соsx)=sinx.
1-(1/5)·cosx=sin²x,
1-(1/5)·cosx=1-cos²x,
(1/5)cosx=cos²x,
cos²x-(1/5)cosx=0,
5cos²x-cosx=0,
cosx(cosx-1)=0,
cosx=0 или cosx=1,
x1=π/2 +πn,
x2=πn, n∈Z.