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For `theta in (=,pi/2),p rov et h a tint_0^theta"log"(1+tanthetatanx)dx=thetalog(sectheta)` |
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Answer» `I=int_(0)^(theta)log(1+tan theta tan x) dx` `=int_(0)^(theta)log(1+tan theta tan (theta-x))dx` `=int_(0)^(theta)log(1+(tantheta(tan theta-tan x))/(1+tan theta tan x))dx` `=int_(0)^(theta)"log"((1+tan^(2)theta))/(1+tan theta tan x)dx` `=int_(0)^(theta)log(1+tan^(2)theta)dx-int_(0)^(theta)log(1+tan theta tan x)dx` `=2theta log sec theta -I` or `2I=2theta log sec theta` or `I=thetalog sec theta` |
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