Question

3sin^2x+10sinxcosx+3cos^2x=0

Answer 1

3(sin^2 x+cos^2 x)+5sin2x=0
3+5sin2x=0
sin2x=-3/5
2x=(-1)^n-1 arcsin3/5+pi n
x=((-1)^n-1 arcsin3/5+pi n)*1/2