\[ y''(x)=2 y(x) \csc ^2(x) \] ✓ Mathematica : cpu = 0.0887688 (sec), leaf count = 64
\[\left \{\left \{y(x)\to \frac {c_1 \cos (x)}{\sqrt {\cos ^2(x)-1}}+\frac {c_2 \left (\cos (x) \log \left (\sqrt {\cos ^2(x)-1}+\cos (x)\right )-\sqrt {\cos ^2(x)-1}\right )}{\sqrt {\cos ^2(x)-1}}\right \}\right \}\] ✓ Maple : cpu = 0.29 (sec), leaf count = 50
\[ \left \{ y \left ( x \right ) ={\frac {-i\ln \left ( \cos \left ( 2\,x \right ) +i\sin \left ( 2\,x \right ) \right ) \sin \left ( 2\,x \right ) {\it \_C2}+{\it \_C1}\,\sin \left ( 2\,x \right ) +2\,{\it \_C2}\, \left ( \cos \left ( 2\,x \right ) -1 \right ) }{\cos \left ( 2\,x \right ) -1}} \right \} \]