Which of the following statements are correct ? (A) $\tan^{-1}x+\tan^{-1}y=\tan^{-1}\left(\frac{x+y}{1-xy }\right), xy < 1 $ (B) $\tan^{-1}x+\tan^{-1}y = \pi + \tan^{-1}\left(\frac{x+y}{1-xy }\right), xy > 1 $ (C) $\sin^{-1}x+\cos^{-1}x=\frac{\pi }{2} , x \in (-1, 1)$ (D) $\tan^{-1}x+\cot^{-1}x=\frac{\pi }{2} , x \in R$ (E) $\cos^{-1}(-x) =-\cos^{-1}x, x \in [-1, 1]$ Choose the correct answer from the options given below : |
(A), (C), (D) Only (A), (B) Only (D), (E) Only (A), (D), (E) Only |
(A), (C), (D) Only |
$(A)\quad \tan^{-1}x+\tan^{-1}y=\tan^{-1}\left(\frac{x+y}{1-xy}\right)$ holds only when $xy<1$ and sum lies in principal range $(A)\ \text{is correct}$ $(B)\quad \tan^{-1}x+\tan^{-1}y=\pi+\tan^{-1}\left(\frac{x+y}{1-xy}\right)\ \text{is not generally valid for }xy>1$ $(B)\ \text{is false}$ $(C)\quad \sin^{-1}x+\cos^{-1}x=\frac{\pi}{2},\ x\in[-1,1]$ Given $x\in(-1,1)$, relation holds $(C)\ \text{is correct}$ $(D)\quad \tan^{-1}x+\cot^{-1}x=\frac{\pi}{2},\ x\in\mathbb{R}$ $(D)\ \text{is correct}$ $(E)\quad \cos^{-1}(-x)=\pi-\cos^{-1}x\neq -\cos^{-1}x$ $(E)\ \text{is false}$ Correct statements are (A), (C), (D). |