What Identity should I use to solve this.
$\displaystyle csc x-\frac{cotx}{secx} =sinx$
as already mentioned...
$\displaystyle
\frac{1}{\sin{\theta}}
-\frac
{\frac{\cos{\theta}}{\sin{\theta}}}
{\frac{1}{\cos{\theta}}}
\rightarrow
\frac{1}{\sin{\theta}}-\frac{\cos{\theta}}{\sin{\theta}}
\frac{\cos{\theta}}{1}
\rightarrow
\frac{1-\cos^2{\theta}}{\sin{\theta}}
\rightarrow
\frac{\sin^2{\theta}}{\sin{\theta}}= \sin{\theta}
$
EDITprobably already got this