\[ \boxed { {\frac {{\rm d}^{2}}{{\rm d}{x}^{2}}}y \left ( x \right ) =-{\frac {\cos \left ( x \right ) {\frac {\rm d}{{\rm d}x}}y \left ( x \right ) }{\sin \left ( x \right ) }}-1/4\,{\frac { \left ( -17\, \left ( \sin \left ( x \right ) \right ) ^{2}-1 \right ) y \left ( x \right ) }{ \left ( \sin \left ( x \right ) \right ) ^{2}}}=0} \]
Mathematica: cpu = 0.090511 (sec), leaf count = 37 \[ \left \{\left \{y(x)\to \frac {c_1 e^{-2 x}}{\sqrt {\sin (x)}}+\frac {c_2 e^{2 x}}{4 \sqrt {\sin (x)}}\right \}\right \} \]
Maple: cpu = 0.046 (sec), leaf count = 25 \[ \left \{ y \left ( x \right ) ={{\it \_C1}\,\sinh \left ( 2\,x \right ) { \frac {1}{\sqrt {\sin \left ( x \right ) }}}}+{{\it \_C2}\,\cosh \left ( 2\,x \right ) {\frac {1}{\sqrt {\sin \left ( x \right ) }}}} \right \} \]