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Question: Range of f(x) = sin<sup>-1</sup>x + tan<sup>-1</sup>x + cos<sup>−1</sup>x is...

Range of f(x) = sin-1x + tan-1x + cos−1x is

A

(0,3π2)\left( 0 , \frac { 3 \pi } { 2 } \right)

B

(π2,3π2)\left( \frac { \pi } { 2 } , \frac { 3 \pi } { 2 } \right)

C

(π2,3π2]\left( - \frac { \pi } { 2 } , \frac { 3 \pi } { 2 } \right]

D

[π4,3π4]\left[ \frac { \pi } { 4 } , \frac { 3 \pi } { 4 } \right]

Answer

[π4,3π4]\left[ \frac { \pi } { 4 } , \frac { 3 \pi } { 4 } \right]

Explanation

Solution

Clearly the domain of the function is [-1, 1]. We know that tan−1 x ∈ [π4,π4]\left[ - \frac { \pi } { 4 } , \frac { \pi } { 4 } \right] for

x ∈ [-1, 1]. Thus range is [π4,3π4]\left[ \frac { \pi } { 4 } , \frac { 3 \pi } { 4 } \right]