5sinx2x-11sin^2 x+3=0 7cos2x-10sinx-3=0
7cos2x-10sinx-3=0 7(cos^2x-sin^2x)-10sinxs-3=0 7(1-sin^2x)-10sinx-3=0 14sin^2x+10sinx-4=0 sinx=t 14t^2+10t-4=0 t1=-1 t2=2/7 sinx=-1 =>x=-pi/2+2pi n sinx=2/7 =>x=(-1)^n arcsin2/7+pi n