Question

cos^2y+4 sin^2y=2 sin 2y

Answer 1

cos^2y+4 sin^2y=2 sin 2y
cos^2y+4 sin^2y=4 sin ycosy (разделим на tg^2)
1+4 tg^2(y)-4 tg(y)=0
4 tg^2(y)-4 tg(y)+1=0
D=16-4*4*1=0
tg(y)=4/8=1/2
y=arctg(1/2)+pi*k