Step-by-step explanation:
[tex]\csc y - \sin y = \dfrac{1}{\sin y} - \sin y[/tex]
[tex]\:\:\:\:\:\:\:\:=\dfrac{1 - \sin^2y}{\sin y}[/tex]
[tex]\:\:\:\:\:\:\:\:= \dfrac{\cos^2y}{\sin y}[/tex]
[tex]\:\:\:\:\:\:\:\:=\cos y \left(\dfrac{\cos y}{\sin y}\right)[/tex]
[tex]\:\:\:\:\:\:\:\:= \cos y \cot y[/tex]
