0} \atop {\cos x>0}} \right. \ \left \{ {{\sin^22x+1>0,\ \forall x} \atop {-\frac{\pi}{2}+2\pi k0} \atop {\cos x>0}} \right. \ \left \{ {{\sin^22x+1>0,\ \forall x} \atop {-\frac{\pi}{2}+2\pi k
\ 0\ t\in(0;1];\\
8(1-t)t+1=10t;\\
8t-8t^2+1=10t;\\
8t^2+2t-1=0;\\
D=2^2-4\cdot8\cdot(-1)=4+32=36=(\pm6)^2;\\
t_1=\frac{-2-6}{16}<0\notin(0;1];\\
t_1=\frac{-2+6}{16}=\frac{4}{16}=\frac14\tin(0;1];\\
\cos^2x=\frac14;\\
\cos x>0;\\
\cos x=\frac12;\\
x=\pm\frac\pi3+2\pi n, n\in Z" alt="8\sin^2x\cos^2x+1=10\cos^2x;\\
8(1-\cos^2x)\cos^2x+1=10\cos^2x;\\
t=\cos^2x==>\ 0\ t\in(0;1];\\
8(1-t)t+1=10t;\\
8t-8t^2+1=10t;\\
8t^2+2t-1=0;\\
D=2^2-4\cdot8\cdot(-1)=4+32=36=(\pm6)^2;\\
t_1=\frac{-2-6}{16}<0\notin(0;1];\\
t_1=\frac{-2+6}{16}=\frac{4}{16}=\frac14\tin(0;1];\\
\cos^2x=\frac14;\\
\cos x>0;\\
\cos x=\frac12;\\
x=\pm\frac\pi3+2\pi n, n\in Z" align="absmiddle" class="latex-formula">