integration tutorial: analysis

Consider the integral
int 2z cos(3z) dz
This is an indefinite integral, so we need to find the most general antiderivative of the integrand f(z).
To find an antiderivative of f(z), 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 use integration by parts to rewrite the product of u = z and v' = cos(3z) in the integrand using the integration by parts formula. This is shown below.
Integration by parts:
Let u = z and v' = cos(3z). Then u' = 1 and v = (1/3) sin(3z), so, remembering the integration by parts formula
int u v' dz = u v - int u' v dz,
we have
int 2z cos(3z) dz = (z) ((1/3) sin(3z)) - int (1) ((1/3) sin(3z)) dz = 2((1/3) z sin(3z) + (1/9) cos(3z)) + 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.