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# Choose the correct option. Justify your answer$9{\sec ^2}A - 9{\tan ^2}A =$A) 1B) 9C) 8D) 0

Last updated date: 27th Mar 2023
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Hint: Here, we will solve the given trigonometric equation by the use of the trigonometric identity ${\sec ^2}A - {\tan ^2}A = 1$ and trigonometric formulae.
$9{\sec ^2}A - 9{\tan ^2}A \to (1)$
Let us common $9$ from equation (1), we get
$\Rightarrow 9({\sec ^2}A - {\tan ^2}A) \to (2)$
Since, we know the trigonometric identity i.e.., ${\sec ^2}A - {\tan ^2}A = 1$. Therefore, equation (2) can be written as
$\Rightarrow 9(1) = 9$
Hence, the value of $9{\sec ^2}A - 9{\tan ^2}A$ is $9$.
Note: The elaborate approach for the given equation is by substituting $\sec A$ with $\dfrac{1}{{\cos A}}$ and $\tan A$ with $\dfrac{{\sin A}}{{\cos A}}$ .