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MathGroup Archive 1993

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Re: Integration bug?

  • To: mathgroup at yoda.physics.unc.edu
  • Subject: Re: Integration bug?
  • From: Steven M. Christensen <stevec at yoda.physics.unc.edu>
  • Date: Thu, 1 Apr 93 22:38:35 EST

Here is how I would handle the previous Integration:

In[1]:= Log[x]/((x - y)*(x - z))

            Log[x]
Out[1]= ---------------
        (x - y) (x - z)

In[2]:= Apart[%,x]

               Log[x]              Log[x]
Out[2]= -(----------------) + ----------------
          (-x + y) (y - z)    (y - z) (-x + z)

In[3]:= Integrate[%[[1]],{x,0,Infinity}] + Integrate[%[[2]],{x,0,Infinity}]

             2         1 2       2         1 2
        -2 Pi  + 3 Log[-]    2 Pi  - 3 Log[-]
                       y                   z
Out[3]= ------------------ + -----------------
            6 (-y + z)          6 (-y + z)

In[4]:= Expand[%]

             1 2          1 2
         Log[-]       Log[-]
             y            z
Out[4]= ---------- - ----------
        2 (-y + z)   2 (-y + z)

In[5]:= Together[%]

             1 2       1 2
        -Log[-]  + Log[-]
             y         z
Out[5]= ------------------
            2 (y - z)

In[6]:= Quit





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