Pregunta: 1−siny1+siny−1+siny1−siny=4tany⋅secy

Prove that :- $\frac{1+\sin \mathrm{y}}{1-\sin \mathrm{y}}-\frac{1-\sin \mathrm{y}}{1+\sin \mathrm{y}}=4\tan \mathrm{y}.\sec \mathrm{y}$

Solution :- combine the two terms by

$\frac{1+\sin \mathrm{y}}{1-\sin \mathrm{y}}-\frac{1-\sin \mathrm{y}}{1+\sin \mathrm{y}}\dots \left(1\right)$