Q.

The value of e-π4+∫0π4e-xtan50x dx∫0π4e-x(tan49x+tan51x) dx is:            [2023]

1 51  
2 49  
3 25  
4 50  

Ans.

(4)

e-π/4+∫0π/4e-xtan50x dx∫0π/4e-x(tan49x+tan51x)dx

First, simplify, ∫0π/4e-xtan50xdx

=[-e-x(tanx)50]0π/4+∫0π/4e-x(50)tan49x·sec2x dx

=-e-π/4+0+50∫0π/4e-x(tanx)49(1+tan2x) dx

=-e-π/4+50∫0π/4e-x[(tanx)51+(tanx)49]dx

Now, -e-π/4+∫0π/4e-x(tanx)50dx∫0π/4e-x(tan49x+tan51x)dx

=50∫0π/4e-x(tan51x+tan49x)dx∫0π/4e-x(tan49x+tan51x)dx=50

∴  e-π/4+∫0π/4e-xtan50x dx∫0π/4e-x(tan49x+tan51x)dx=50