Sin^2 3x + sinx+cos^2 3x=0
Sin²3x+sinx+cos²3x=0 (sin²3x+cos²3x)+sinx=0 1+sinx=0 sinx=-1 x=3π/2+2πn, n∈Z
(sin²3x+cos²3x) +sinx=0 sinx=-1 x=-π/2+2πn, n € Z