Contour integration of real functions

[stefaneli]

I have a problem with choosing a contour for integration... Can someone explain to me when to use a keyhole contour and when a semi-circle? Thanks...:)

 

[joeblow]

I have a problem with choosing a contour for integration... Can someone explain to me when to use a keyhole contour and when a semi-circle? Thanks...:)

Use keyhole when you need to avoid singularities.

 

[stefaneli]

Singularities on real axis?

 

[joeblow]

Yes. Like (sin x)/x.

 

[stefaneli]

Thanks man.:)