(a) Show that

\(\frac{1}{\operatorname{cosec}\theta-1}+ \frac{1}{\operatorname{cosec}\theta+1} =2\sin\theta\,\operatorname{sec}^2\theta.\)

(b) Hence solve the equation

\(\frac{1}{\operatorname{cosec}2\phi-1}+ \frac{1}{\operatorname{cosec}2\phi+1} =4\sin2\phi,\)

for \(-90^\circ\leq\phi\leq90^\circ\).