Question

cos(2pi-2/3x)+cos(pi/2-2/3x)=0

Answer 1

cos(2pi-2/3x)+cos(pi/2-2/3x)=0

cos2/3x+sin2/3x=0  поделим  на cos2/3x

1+tg2/3x=0

tg2/3x=-1

2/3x=-pi/4+pi n

x=3/2*(-pi/4)+3/2pi n

x-3pi/8+3/2pi n  neZ