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Match List-I with List-II

List-IList-II
(Inverse Trigonometric Function)(Principal Value)
(A) sin⁡−1(−12)\sin^{-1}(-\frac{1}{2})(I) π/6{\pi}/{6}
(B) cos⁡−1(−12)\cos^{-1}(-\frac{1}{2})(II) −π/6-{\pi}/{6}
(C) tan⁡−1(−3)\tan^{-1}(-\sqrt{3})(III) 2π/3{2\pi}/{3}
(D) cot⁡−1(3)\cot^{-1}(\sqrt{3})(IV) −π/3-{\pi}/{3}

Choose the correct answer from the options given below:

Solution

✅ Correct Option: 3

Principal value ranges for inverse trigonometric functions:

sin⁡−1(x)\sin^{-1}(x): [−π2,π2][-\frac{\pi}{2}, \frac{\pi}{2}]

cos⁡−1(x)\cos^{-1}(x): [0,π][0, \pi]

tan⁡−1(x)\tan^{-1}(x): (−π2,π2)(-\frac{\pi}{2}, \frac{\pi}{2})

cot⁡−1(x)\cot^{-1}(x): (0,π)(0, \pi)


For sin⁡−1(−12)\sin^{-1}(-\frac{1}{2}):

Need an angle in [−π2,π2][-\frac{\pi}{2}, \frac{\pi}{2}] whose sine equals −12-\frac{1}{2}.

Since sin⁡(π6)=12\sin(\frac{\pi}{6}) = \frac{1}{2} and sine is negative for negative angles:

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

Therefore, sin⁡−1(−12)=−π6\sin^{-1}(-\frac{1}{2}) = -\frac{\pi}{6} → (II)


For cos⁡−1(−12)\cos^{-1}(-\frac{1}{2}):

Need an angle in [0,π][0, \pi] whose cosine equals −12-\frac{1}{2}.

Since cos⁡(π3)=12\cos(\frac{\pi}{3}) = \frac{1}{2} and cosine is negative in the second quadrant:

π−π3\pi - \frac{\pi}{3}

=3π−π3= \frac{3\pi - \pi}{3}

=2π3= \frac{2\pi}{3}

Therefore, cos⁡−1(−12)=2π3\cos^{-1}(-\frac{1}{2}) = \frac{2\pi}{3} → (III)


For tan⁡−1(−3)\tan^{-1}(-\sqrt{3}):

Need an angle in (−π2,π2)(-\frac{\pi}{2}, \frac{\pi}{2}) whose tangent equals −3-\sqrt{3}.

Since tan⁡(π3)=3\tan(\frac{\pi}{3}) = \sqrt{3}:

tan⁡(−π3)=−3\tan(-\frac{\pi}{3}) = -\sqrt{3}

Therefore, tan⁡−1(−3)=−π3\tan^{-1}(-\sqrt{3}) = -\frac{\pi}{3} → (IV)


For cot⁡−1(3)\cot^{-1}(\sqrt{3}):

Need an angle in (0,π)(0, \pi) whose cotangent equals 3\sqrt{3}.

cot⁡(π6)\cot(\frac{\pi}{6})

=cos⁡(π6)sin⁡(π6)= \frac{\cos(\frac{\pi}{6})}{\sin(\frac{\pi}{6})}

=3212= \frac{\frac{\sqrt{3}}{2}}{\frac{1}{2}}

=3= \sqrt{3}

Therefore, cot⁡−1(3)=π6\cot^{-1}(\sqrt{3}) = \frac{\pi}{6} → (I)


Final matching:

FunctionPrincipal Value
(A) sin⁡−1(−12)\sin^{-1}(-\frac{1}{2})(II) −π6-\frac{\pi}{6}
(B) cos⁡−1(−12)\cos^{-1}(-\frac{1}{2})(III) 2π3\frac{2\pi}{3}
(C) tan⁡−1(−3)\tan^{-1}(-\sqrt{3})(IV) −π3-\frac{\pi}{3}
(D) cot⁡−1(3)\cot^{-1}(\sqrt{3})(I) π6\frac{\pi}{6}

Correct answer: (A)-(II), (B)-(III), (C)-(IV), (D)-(I)

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