Complex Analysis: Integral of log(x)/(x+1)^2

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Today, we integrate log(x)/(x+1)^2 from 0 to infinity using the keyhole contour.
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This channel is awesome af, please continue and don't stop, we'll always support you.

Thor-ykcr
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It's me, when you obtained I=0 : 🤔
And ...
It's me, at the end of video: 🤓🤓
Great, as always (especially the second part, when you proved those integral are equal by Zero) ...
Thank you so much dear *QN³*

wuyqrbt
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For a simpler method, substitute u=1/x, move around some things and replace u with x and you'll see that the integral is equal to its negative

buddychumpalfriendhomiebud
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Saving me complex final grade. Idk why we are doing so many hard contours for a one semester class. My school is jamming complex 1 and 2 into a semester lmaooo

austinvera
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It may be a good example to illustrate contour integration. However if you set J(a) = ∫Log[a*x]/(1+x)^2, (same limits), then
J ' [a]= 1/a *∫1/(1+x)^2 (0 to inf ) = 1/a . Thus J[a]= Log[a], but for a=1 we find J[1] = 0.

renesperb
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Perfect explanation! … “in particular” the limits part of the video !

saeida.alghamdi
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How draw graph complex function in complex plane

ayushtharollno
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This is not very convincing. The limits in the end for big gamma are not the same as for little gamma - since r remains in the denominator and goes to infinity in the second case. The argument for big gamma to yield zero is that log r “swared” grows slower than r - and that needs to be shown. The reference to the calculations before seems confusing to me.

matthias
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Great!

Can we try to evaluate ∫(0→∞)(ln(x) /(1-x^2) dx using the keyhole contour? Best regards.

George-ijgm