Trigonometric Equations Question 348

Question: If $ 3({{\sec }^{2}}\theta +{{\tan }^{2}}\theta )=5 $ , then the general value of $ \theta $ is

Options:

A) $ 2n\pi +\frac{\pi }{6} $

B) $ 2n\pi \pm \frac{\pi }{6} $

C) $ n\pi \pm \frac{\pi }{6} $

D) $ n\pi \pm \frac{\pi }{3} $

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Answer:

Correct Answer: C

Solution:

  • $ {{\sec }^{2}}\theta +{{\tan }^{2}}\theta =\frac{5}{3} $ , also $ {{\sec }^{2}}\theta -{{\tan }^{2}}\theta =1 $
    $ \Rightarrow $ $ {{\tan }^{2}}\theta =\frac{1}{3}={{\tan }^{2}}( \frac{\pi }{6} )\Rightarrow \theta =n\pi \pm \frac{\pi }{6} $ .