If \(\cot \theta + \tan \theta = y\) and \(\sec \theta - \cos \theta = z\), then check that \((y^2 z)^{\frac{2}{3}} - (y z^2)^{\frac{2}{3}} = 1\).
 
Proof:
 
\(y = \cot \theta + \tan \theta\)
 
Simplifying, we get:
 
\(y =\)
 
\(z = \sec \theta - \cos \theta\)
 
\(z =\)
 
\(y^2z=\)
 
\(yz^2=\)
 
\((y^2 z)^{\frac{2}{3}}=\)
 
\((y z^2)^{\frac{2}{3}} =\)
 
\((y^2 z)^{\frac{2}{3}} - (y z^2)^{\frac{2}{3}} = 1\)
 
Thus, LHS \(=\) RHS.
 
Hence, we proved.
Answer variants:
\(\frac{1}{\cos^2 \theta}\)
\(\frac{\sin^2 \theta}{\cos \theta}\)
\(\frac{\sin^3 \theta}{\cos^3 \theta}\)
\(\frac{1}{\cos^3 \theta}\)
\(\frac{\sin^2 \theta}{\cos^2 \theta}\)
\(\frac{1}{\sin \theta \cos \theta}\)