Question
Prove the following identity : $\frac{\left(1+\tan ^2 A\right) \cot A}{\cos e c^2 A}=\tan A$

Answer

$\frac{\left(1+\tan ^2 A\right) \cot A}{\cos e c^2 A}$
$=\frac{\sec ^2 A \cot A}{\operatorname{cosec} 2} \ldots \ldots\left(\therefore \sec ^2 A=1+\tan ^2 A\right)$
$=\frac{\frac{1}{\cos ^2 A} \cdot \frac{\cos A}{\sin A}}{\frac{1}{\sin ^2 A}}=\frac{1}{\frac{\cos A \sin A}{\frac{1}{\sin ^2 A}}}$
$=\frac{\sin A}{\cos A}=\tan A$

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