Trigonometric-Equations Question 398

Question: If $ \tan (\pi \cos \theta )=\cot (\pi \sin \theta ) $ , then $ \sin ( \theta +\frac{\pi }{4} ) $ equals

[AMU 1999]

Options:

A) $ \frac{1}{\sqrt{2}} $

B) $ \frac{1}{2} $

C) $ \frac{1}{2\sqrt{2}} $

D) $ \frac{\sqrt{3}}{2} $

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Answer:

Correct Answer: A

Solution:

  • $ \tan (\pi \cos \theta )=\tan ( \frac{\pi }{2}-\pi \sin \theta ) $
    $ \therefore \sin \theta +\cos \theta =\frac{1}{2} $
    Þ $ \sin ( \theta +\frac{\pi }{4} )=\frac{1}{2\sqrt{2}} $ .