Question

Решите уравнение cos(2π-2/3 x) + cos(π/2-2/3 x)=0

Answer 1

cos(2π-2/3x)+cos(π/2-2/3x)=0
cos2/3x+sin2/3x=0/cos2/3x
1+tg2/3x=0
tg2/3x=-1
2/3x=-π/4+πn
x=-3π/8+3πn/2,n∈z