integration tutorial: analysis

Consider the integral
int [ e3m - 1 / em + 1 ] dm
This is an indefinite integral, so we need to find the most general antiderivative of the integrand f(m).
To find an antiderivative of f(m), we go through our list of integration methods:
  1. Recognize elementary antiderivatives
  2. Rewrite the integrand to make it easier
  3. Use substitution to reverse the chain rule or simplify the integrand
  4. Use integration by parts
  5. Use inspection to see the value of a definite integral
to find one that works for this integrand. In this case, only one method is appropriate. We can rewrite the integrand: use properties of the exponents to give an expression that is more easily integrable. This is shown below.
Rewriting:
Use properties of the exponents to rewrite the integral:
[ e3m - 1 / em + 1 ] = e2m - 2.
Thus,
int [ e3m - 1 / em + 1 ] dm =inte2m - 2dm
which can be evaluated using substitution, to obtain
inte2m - 2dm = ((1/2) e2m - 2) + C.

Explanation for rewritten term(s)
Substitution
Let w = 2m - 2. Then w' = 2, so (1/2) dw = dm. The integral can therefore be rewritten as
int e2m - 2 dm = int ew (1/2) dw = (1/2) ew + C
Thus, substituting back for w,
int e2m - 2 dm = (1/2) e2m - 2 + C

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integration analysis
Last Modified: Wed Feb 6 13:53:59 EST 2002
Comments to glarose@umich.edu
©2002 Gavin LaRose, UM Math Dept.