0\\
cosx<\frac{4}{5}\\
8-10cosx=4(1-cos^2x)\\\
8-10cosx=4-4cos^2x\\
4cos^2x-10cosx+4=0\\
D=100-4*4*4=6^2\\
x=\frac{10+6}{8}=2>1\\
x=\frac{10-6}{8}=\frac{1}{2}\\
x=\frac{\pi}{3}+2\pi*k\\
" alt="\sqrt{8-10cosx}=2sinx\\
8-10cosx=4sin^2x\\
8-10cosx>0\\
cosx<\frac{4}{5}\\
8-10cosx=4(1-cos^2x)\\\
8-10cosx=4-4cos^2x\\
4cos^2x-10cosx+4=0\\
D=100-4*4*4=6^2\\
x=\frac{10+6}{8}=2>1\\
x=\frac{10-6}{8}=\frac{1}{2}\\
x=\frac{\pi}{3}+2\pi*k\\
" align="absmiddle" class="latex-formula">