3+sin2x=4sin^2x
sin2x=2sinx*cosx
3+2sinx*cosx=4sin^2x Делим на sin^2x
3/sin^2x + 2ctgx =4
1/sin^2x=1+ctg^2x
3(1+ctg^2x)+2ctgx=4
3ctg^2x+2ctgx-1=0
D=4+12=16
ctgx=1/3 -> x=arcctg 1/3 + pi*k
ctgx=-1 ->x=3pi/4+pi*l
