jee-main 2022 Q74
Integral Equation to Determine a Function Value
Let $g : ( 0 , \infty ) \rightarrow R$ be a differentiable function such that $\int \left( \frac { x \cos x - \sin x } { e ^ { x } + 1 } + \frac { g(x) ( e ^ { x } + 1 ) - x e ^ { x } } { ( e ^ { x } + 1 ) ^ { 2 } } \right) \mathrm { d } x = \frac { x g(x) } { e ^ { x } + 1 } + C$, for all $x > 0$, where $C$ is an arbitrary constant. Then
(1) $g$ is decreasing in $\left( 0 , \frac { \pi } { 4 } \right)$
(2) $g - g ^ { \prime }$ is increasing in $\left( 0 , \frac { \pi } { 2 } \right)$
(3) $g ^ { \prime }$ is increasing in $\left( 0 , \frac { \pi } { 4 } \right)$
(4) $g + g ^ { \prime }$ is increasing in $\left( 0 , \frac { \pi } { 2 } \right)$