Cos(5x-π/3)=0
5x-π/3=π/2+πn, n∈z
5x=π/2+π/3+πn, n∈z
5x=5π/6+πn, n∈z
x=π/6+π/5n, n∈z
при n=-1; x=π/6-π/5= -π/30
Ответ. x= -π/30
cos(5x-60°)=0
5x-60°=90°+180°n, n∈z
5x=90°+60°+180°n, n∈z
5x=150°+180°n, n∈z
x=30°+36°n, n∈z
при n=-1; x=30°-36°= -6°
Ответ. x= -6°