3sin^2 2x + 10sin2x + 3 = 0
1) sin 2x =t
2) 3t^2 + 10 t + 3 =0
D= 10^2 - 4×3×3 =100-36=64=8^2
t1= -10-8/6=-18/6=-2
t2= -10+8/6=-2/6=-1/3
3) sin2x = -2
sin2x = - 1/3
