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The value of tan⁡−1(1)+cos⁡−1(−32)+sin⁡−1(12)\tan^{-1}(1) + \cos^{-1}\left(-\frac{\sqrt{3}}{2}\right) + \sin^{-1}\left(\frac{1}{2}\right) is

Solution

✅ Correct Option: 1

The angle with tangent value of 1 occurs when opposite = adjacent, which happens at 45° or π4\frac{\pi}{4} radians.

tan⁡−1(1)=π4\tan^{-1}(1) = \frac{\pi}{4}


For cosine value of −32-\frac{\sqrt{3}}{2}, the negative sign indicates the 2nd or 3rd quadrant. The range of inverse cosine is [0,π][0, \pi], so the 2nd quadrant is used.

Since cos⁡(π6)=32\cos\left(\frac{\pi}{6}\right) = \frac{\sqrt{3}}{2}

In the 2nd quadrant:

π−π6=5π6\pi - \frac{\pi}{6} = \frac{5\pi}{6}

cos⁡−1(−32)=5π6\cos^{-1}\left(-\frac{\sqrt{3}}{2}\right) = \frac{5\pi}{6}


The sine value of 12\frac{1}{2} is a standard value:

sin⁡(π6)=12\sin\left(\frac{\pi}{6}\right) = \frac{1}{2}

sin⁡−1(12)=π6\sin^{-1}\left(\frac{1}{2}\right) = \frac{\pi}{6}


Adding all three values:

π4+5π6+π6\frac{\pi}{4} + \frac{5\pi}{6} + \frac{\pi}{6}

Converting to common denominator of 12:

3π12+10π12+2π12\frac{3\pi}{12} + \frac{10\pi}{12} + \frac{2\pi}{12}

=15π12= \frac{15\pi}{12}

=5π4= \frac{5\pi}{4}

Therefore, the value is 5π4\frac{5\pi}{4}.

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