2)
sin(2x)=cos(3x)
sin(2x)=cos(2x+x)
sin(2x)=sos(2x)*cos(x)-sin(2x)*sin(x)
sin(2x)=(1-2sin^2(x))*cos(x)-2sin(x)*cos(x)*sin(x)
sin(2x)=cos(x)-2sin^2(x)*cos(x)-2sin^2(x)*cos(x)
sin(2x)=cos(x)-4sin^2(x)*cos(x)
2sin(x)*cos(x)=cos(x)-4sin^2(x)*cos(x)
cos(x)*[2sin(x)+4sin^2(x)-1]=0
1.cos(x)=0
x=pi/2+pi*n
2. 4sin^2(x)+2sin(x)-1=0
sin(x)=t
4t^2+2t-1=0
D=b^2-4ac=4+17=21
t1,2=(-b±sqrt(D))/2a
t1=(-2+sqrt(21)/8
t2=(-2-sqrt(21)/8
sin(x)=(-2+sqrt(21))/8
x=(-1)^n*arcsin(-2+sqrt(21))/8+pi*n
sin(x)=(-2-sqrt(21))/8
x=(-1)^n*arcsin(-2-sqrt(21))/8+pi*n