Sometimes, along the way, one of the
integrals you get (in the form   ) is the same as the original 
function that you wanted to integrate.  In this case, a little algebra will
produce the result you are trying to find.  Try integrating
 ) is the same as the original 
function that you wanted to integrate.  In this case, a little algebra will
produce the result you are trying to find.  Try integrating   .
 .
  
 
At this point, we let   and
  and   so 
that
  so 
that   and
  and   .  This gives 
us
 .  This gives 
us
  
 
Now we simply add   to both sides of the equation
and divide by two to get
  to both sides of the equation
and divide by two to get
 