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Discontinuities of this kind have infinite derivatives at the point of discontinuities 
  and can lead to problems with integration as well. The difficulties with integration 
  are sometimes avoidable , because the area under a curve may be finite even 
  if the curve goes to infinity. This does not happen form the function  
  
, 
  the area under which is infinite for x > 0.
However, if we want to integrate from a to b with a<0 and b>0, this can be defined, using the fact that the infinite part above 0 cancels symmetrically with the infinite part below.
Thus you can define the "principal part" of the integral by excluding the contribution from -c to c in the limit as c goes to 0.
  
which 
  limit exists.