(a) Show that

\(\displaystyle \frac{\operatorname{cot}\theta+\tan\theta}{\operatorname{sec}\theta}=\operatorname{cosec}\theta.\)

(b) Hence solve the equation

\(\displaystyle \left(\frac{\operatorname{cot}\left(\frac{\phi}{3}\right)+\tan\left(\frac{\phi}{3}\right)}{\operatorname{sec}\left(\frac{\phi}{3}\right)}\right)^2=2\)

for \(-540^\circ\lt\phi\lt540^\circ\).