JEE Advanced · Mathematics · 8. Trigonometric Equations
The number of solutions of the pair of equations \(2 \sin ^2 \theta-\cos 2 \theta=0\) and \(2 \cos ^2 \theta-3 \sin \theta=0\) in the interval \([0,2 \pi]\) is
- A zero
- B one
- C two
- D four
Answer & Solution
Correct Answer
(C) two
Step-by-step Solution
Detailed explanation
\(2 \sin ^2 \theta-\cos 2 \theta=0 \Rightarrow \sin ^2 \theta=\frac{1}{4}\)
Also, \(2 \cos ^2 \theta=3 \sin \theta \Rightarrow \sin \theta=\frac{1}{2}\)
\(\Rightarrow\) Two solutions in \([0,2 \pi]\).
Also, \(2 \cos ^2 \theta=3 \sin \theta \Rightarrow \sin \theta=\frac{1}{2}\)
\(\Rightarrow\) Two solutions in \([0,2 \pi]\).
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