Question:

The value of \[ \tan\left(\frac{7\pi}{8}\right) \] is

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Remember the identity: \[ \tan(\pi-\theta)=-\tan\theta \] Also, \[ \tan\left(\frac{\pi}{8}\right)=\sqrt{2}-1 \] is a standard trigonometric value.
Updated On: Jun 22, 2026
  • \(\sqrt{2}-1\)
  • \(1-\sqrt{2}\)
  • \(1+\sqrt{2}\)
  • \(\dfrac{1}{1+\sqrt{2}}\)
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The Correct Option is B

Solution and Explanation

Step 1: Rewrite the angle.
We have \[ \frac{7\pi}{8} = \pi-\frac{\pi}{8} \] Using the identity \[ \tan(\pi-\theta)=-\tan\theta, \] we get \[ \tan\left(\frac{7\pi}{8}\right) = -\tan\left(\frac{\pi}{8}\right) \]

Step 2: Find the value of \(\tan\left(\frac{\pi}{8}\right)\).
Using the standard identity, \[ \tan\left(\frac{\pi}{8}\right) = \sqrt{2}-1 \] Therefore, \[ \tan\left(\frac{7\pi}{8}\right) = -(\sqrt{2}-1) \] \[ =1-\sqrt{2} \]

Step 3: Final conclusion.
Hence, \[ \boxed{1-\sqrt{2}} \] which corresponds to option (2).
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