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?
Only I
Only II
Both I and II
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.