Question: If $ \sin \theta =\frac{a^{2}-1}{a^{2}+1}, $ then the value of $ \sec \theta +\tan \theta $ will be
Options:
A) $ \frac{a}{\sqrt{2}} $
B) $ \frac{a}{a^{2}+1} $
C) $ \sqrt{2}a $
D) $ a $
Show Answer
Answer:
Correct Answer: D
Solution:
- $ \sin \theta =\frac{a^{2}-1}{a^{2}+1} $
In $ \Delta ABC, $
$ BC=\sqrt{{{(AC)}^{2}}-{{(AB)}^{2}}} $
$ =\sqrt{{{(a^{2}+1)}^{2}}-{{(a^{2}-1)}^{2}}} $
$ =\sqrt{a^{4}+1+2a^{2}-a^{4}-1+2a^{2}} $
$ =\sqrt{4a^{2}}=2a $
$ \therefore $ $ \sec \theta +tan\theta =\frac{a^{2}+1}{2a}+\frac{a^{2}-1}{2a} $
$ =\frac{a^{2}+1+a^{2}-1}{2a}=\frac{2a^{2}}{2a}=a $