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Question: Answered & Verified by Expert
The most general value of $\theta$ which satisfies both the equations $\tan 8=-1$ and $\cos \theta=\frac{1}{\sqrt{2}}$ is
MathematicsTrigonometric EquationsTS EAMCETTS EAMCET 2011
Options:
  • A $n \pi+\frac{7 \pi}{4}$
  • B $2 n \pi+\frac{7 \pi}{4}$
  • C $n \pi+(-1)^n \frac{7 \pi}{4}$
  • D $\frac{7 n \pi}{4}$
Solution:
1352 Upvotes Verified Answer
The correct answer is: $2 n \pi+\frac{7 \pi}{4}$
Given trigonometric equations are
$\tan \theta=-1$
and
$\cos \theta=\frac{1}{\sqrt{2}}$
$\begin{array}{ll}\Rightarrow & \sin \theta=-1 / \sqrt{2} \\ \Rightarrow & \sin \theta=\sin \frac{7 \pi}{4} \\ \therefore & \theta=2 n \pi+\frac{7 \pi}{4}\end{array}$

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