∫ex+1x(cosx−sinx)dx+∫g(x)(ex+1)2ex+1−xexdx
=ex+1x(sinx+cosx)−∫(ex+1)2ex+1−xex(sinx+cosx)dx+∫g(x)(ex+1)2ex+1−xexdx
By comparison, we get, g(x)=sinx+cosx
⇒g(x)=2[sin(x+4π)]
Since x∈(0,4π) so, x+4π∈(4π,2π)
So g(x) is increasing in (0,4π)
g′(x)=cosx−sinx
i.e. g(x)−g′(x)=2sinx is an increasing function in (0,2π).