Practicing Success
Match List - I with List - II.
Choose the correct answer from the options given below : |
(A) - (IV), (B) - (I), (C) - (III), (D) - (II) (A) - (III), (B) - (II), (C) - (IV), (D) - (I) (A) - (I), (B) - (III), (C) - (IV), (D) - (II) (A) - (II), (B) - (IV), (C) - (I), (D) - (III) |
(A) - (IV), (B) - (I), (C) - (III), (D) - (II) |
(A) $tan^{-1}\sqrt{3}-sec^{-1}(-2)$ Let $tan^{-1}\sqrt{3}=x$ i.e. $tanx=\sqrt{3}⇒tan\frac{\pi}{3}$ $∴x=\frac{\pi}{3}∈[-\frac{\pi}{2},\frac{\pi}{2}]$ Now, let $sec^{-1}(-2) = y$ that is sec y = -2 $∴y=-sec\frac{\pi}{3}$ i.e. $secy=sec(\pi-\frac{\pi}{3})=sec\frac{2\pi}{3}$ Thus, $y = \frac{2\pi}{3}∈(0,π)-(\frac{π}{2})$ Now consider $tan^{-1}\sqrt{3}-sec^{-1}(-2)$ as: $tan^{-1}\sqrt{3}-sec^{-1}(-2)=x-y=\frac{\pi}{3}-\frac{2\pi}{3}=\frac{-\pi}{3}$ (B) $cot^{-1}(\frac{-1}{\sqrt{3}})$ Let $y=cot^{-1}(\frac{-1}{\sqrt{3}})=coty=\frac{-1}{\sqrt{3}}$ $cot y = cot(π-\frac{π}{3})$ we know that range of principal value of $cot^{-1}x$ is (0, π) $y=π-\frac{π}{3}⇒\frac{2π}{3}$ (C) $cos^{-1}(-\frac{1}{\sqrt{2}})$ Let $y = cos^{-1}(-\frac{1}{\sqrt{2}})$ $y =π- cos^{-1}(-\frac{1}{\sqrt{2}})$ $∴cos^{-1}(-x)=π- cos^{-1}x$ Since $cos\frac{π}{4}=\frac{1}{\sqrt{2}}$ $\frac{π}{4}=cos^{-1}(\frac{1}{\sqrt{2}})$ $y =π- cos^{-1}(\frac{1}{\sqrt{2}})$ $y=π-\frac{π}{4}⇒\frac{3π}{4}$ Range of cos-1 is [0, π] Principal value is $\frac{3π}{4}$ (D) $cos^{-1}(\frac{1}{2})+ sin^{-1}(\frac{1}{2})$ $cos^{-1}\frac{1}{2}+sin^{-1}(\frac{1}{2})$ $=\frac{π}{3}+\frac{π}{6}=\frac{2π+π}{6}=\frac{3π}{6}=\frac{π}{2}$ So, (A) - (II), (B) - (IV), (C) - (I), (D) - (III) Option 4 is correct. |