Consider the following statements. I. $\sin ^{-1}\left(y^2-4 y+6\right)+\cos ^{-1}\left(y^2-4 y+6\right)…

Consider the following statements. I. $\sin ^{-1}\left(y^2-4 y+6\right)+\cos ^{-1}\left(y^2-4 y+6\right) =\frac{\pi}{2}, \forall y \in R$ II. $\sec ^{-1}\left(y^2-4 y+6\right)+\operatorname{cosec}^{-1}\left(y^2-4 y+6\right) =\frac{\pi}{2}, \forall y \in R$ Which of the above statement(s) is/are true?
  1. Only I
  2. Only II
  3. Both I and II
  4. Neither I nor II

Solution

Given statements, $\sin ^{-1}\left(y^2-4 y+6\right)+\cos ^{-1}\left(y^2-4 y+6\right)=\frac{\pi}{2}$ $\because y^2-4 y+6=(y-2)^2+2 \geq 2, \forall y \in R \text {. }$ So, statement (i) is false and statement (ii) is true.

Asked in: AP EAMCET 2018 (22 Apr Shift 2)

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