Sin2.5x=

sin1.5x=

cos2.5x=

cos1.5x=

1+cos7x = (sin1,5x-cos1,5x) ^2

1+cos7x=sin ² (1.5x) - 2sin (1.5x) cos (1.5x) + cos² (1.5x)

cos7x=-sin3x

cos7x=cos (3x+π/2)

3x+π/2=±arccos (cos7x) + 2πn

3x+π/2=±7x+2πn

x (3±7) = - π/2+2πn

x = (-π/2+2πn) / (3±7), n∈Z

Ответ:

x = (-π/2+2πn) / 10

x = - (-π/2+2πn) / 4

n∈Z