The function $f ( x ) = \tan ^ { - 1 } ( \sin x + \cos x )$ is an increasing function in
(1) $\left( \frac { \pi } { 4 } , \frac { \pi } { 2 } \right)$
(2) $\left( - \frac { \pi } { 2 } , \frac { \pi } { 4 } \right)$
(3) $\left( 0 , \frac { \pi } { 2 } \right)$
(4) $\left( - \frac { \pi } { 2 } , \frac { \pi } { 2 } \right)$
The function $f ( x ) = \tan ^ { - 1 } ( \sin x + \cos x )$ is an increasing function in\\
(1) $\left( \frac { \pi } { 4 } , \frac { \pi } { 2 } \right)$\\
(2) $\left( - \frac { \pi } { 2 } , \frac { \pi } { 4 } \right)$\\
(3) $\left( 0 , \frac { \pi } { 2 } \right)$\\
(4) $\left( - \frac { \pi } { 2 } , \frac { \pi } { 2 } \right)$