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The Principal value of cos⁡−1(−12)\cos^{-1} \left( -\frac{1}{2} \right) is:

Solution

✅ Correct Option: 2

Principal range of cos⁡−1\cos^{-1} is [0,π][0, \pi].

cos⁡−1(−x)=π−cos⁡−1(x)\cos^{-1}(-x) = \pi - \cos^{-1}(x).

cos⁡−1(−12)=π−π3=2π3\cos^{-1}(-\frac{1}{2}) = \pi - \frac{\pi}{3} = \frac{2\pi}{3}.

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