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JEE Advanced
Exam
JEE Advanced
Subject
Mathematics
Chapter
Trigonometry

JEE Advanced · Mathematics · Trigonometry

If 3 x+ (2 x-(7 π)/(6))=-2 , then x is equal to ( where m ∈ I)

If cos⁡3x+sin⁡(2x−7π6)=−2\cos 3 x+\sin \left(2 x-\frac{7 \pi}{6}\right)=-2, then xx is equal to (( where m∈I)m \in I)

Options

  1. Aπ3(6m−1)\frac{\pi}{3}(6 m-1)
  2. Bπ3(6m+1)\frac{\pi}{3}(6 m+1)
  3. Cπ3(2m+1)\frac{\pi}{3}(2 m+1)
  4. Dnone of these

Correct answer

B. π3(6m+1)\frac{\pi}{3}(6 m+1)

Step-by-step solution

1+cos⁡3x+1−[cos⁡(π2+(2x−7π6))]=02cos⁡23x2+1−cos⁡(2x−2π3)=02cos⁡23x2+2sin⁡2(x−π3)=0\begin{aligned} & 1+\cos 3 x+1-\left[\cos \left(\frac{\pi}{2}+\left(2 x-\frac{7 \pi}{6}\right)\right)\right]=0 \\ & 2 \cos ^2 \frac{3 x}{2}+1-\cos \left(2 x-\frac{2 \pi}{3}\right)=0 \\ & 2 \cos ^2 \frac{3 x}{2}+2 \sin ^2\left(x-\frac{\pi}{3}\right)=0\end{aligned}\cos \frac{3 x}{2}=0, \sin \left(x-\frac{\pi}{3}\right)=0\mathrm{x}=\frac{\pi}{3}, \piandand\mathrm{x}=\frac{\pi}{3}, \frac{2 \pi}{3}, \frac{7 \pi}{3}, \ldots\therefore \mathrm{x}=\frac{\pi}{3}isthecommonvaluewhichsatisfiesbothis the common value which satisfies both\therefore x=2 n \pi+\frac{\pi}{3}=(6 n+1) \frac{\pi}{3}$
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