5sin^2x+6cosx-6=0помогите пожалуйста)

[latex]5sin^2x+6cosx-6=0\\\\5(1-cos^2x)+6cosx-6=0\\\\5-5cos^2x+6cosx-6=0\\\\5cos^2x-6cosx+1=0\\\\5t^2-6t+1=0\; \; ,\; \; D/4=9-5=4\; ,\\\\a)\; \; cosx= \frac{3-2}{5} =\frac{1}{5}\\\\\underline {x=\pm arccos \frac{1}{5}+2\pi n,\; n\in Z }\\\\b)\; \; cosx= \frac{3+2}{5}=1 \\\\\underline {x=2\pi n,\; n\in Z}[/latex]