Question

Find the value of $9{\sec }^{2}A-9{\tan }^{2}A$.

Answer 1

We have, $9{\sec }^{2}A-9{\tan }^{2}A$

Let $r=9{\sec }^{2}A-9{\tan }^{2}A$

$r=9({\sec }^{2}A-{\tan }^{2}A)$

We know that

${\sec }^{2}A-{\tan }^{2}A=1$

Therefore,

$r=9\times 1=9$

Hence, this is the answer.