integration tutorial: analysis

Consider the integral
int 3e2m + 2e3m 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: consider the parts of the integral separately to give an expression that is more easily integrable. This is shown below.
Rewriting:
Consider the parts of the integral separately. This can be broken into separate integrals,
int 3e2m + 2e3m dm =int3e2mdm+int2e3mdm
which can be evaluated using substitution (of "ax"), and substitution (of "ax"), respectively, to obtain
int3e2mdm+int2e3mdm = ((3/2) e2m) + ((2/3) e3m) + C.

Explanation for rewritten term(s)
Substitution (of "ax")
Let w = 2 m. Then w' = 2, so (1/2) dw = dm. The integral can therefore be rewritten as
int 3e2m dm = int 3ew (1/2) dw = (3/2) ew + C
Thus, substituting back for w,
int 3e2m dm = (3/2) e2m + C

Substitution (of "ax")
Let w = 3 m. Then w' = 3, so (1/3) dw = dm. The integral can therefore be rewritten as

int 2e3m dm = int 2ew (1/3) dw = (2/3) ew + C
Thus, substituting back for w,
int 2e3m dm = (2/3) e3m + 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.