What is int_1^(e^(pi/4)) 4/(x(1+(lnx)^2))dxeπ414x(1+(lnx)2)dx?

1 Answer
Mar 16, 2018

4tan^-1(pi/4)4tan1(π4)

Explanation:

I=int_1^(e^(pi/4))4/(x(1+(lnx)^2))dxI=eπ414x(1+(lnx)2)dx
Let, lnx=u=>1/x*dx=dulnx=u1xdx=du
x=1=>u=ln1=>u=0andx=1u=ln1u=0and
x=e^(pi/4)=>u=lne^(pi/4)=>u=pi/4x=eπ4u=lneπ4u=π4
:.I=int_0^(pi/4)4/(1+u^2)du=[4tan^-1u]_0^(pi/4)
:.I=4[tan^-1(pi/4)-tan^-1(0)]=4[tan^-1(pi/4)-0]
:.I=4tan^-1(pi/4)