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Homework Help: Integral - help needed please

  1. Jan 28, 2006 #1
    I have been asked to state which one of the following 3 integrals I can solve using integration by substitution

    (i) integral cos (x^2) dx

    (ii) integral x cos x (x^2) dx

    (iii) integral x^2 cos (x^2) dx

    I would say that it is (ii) because x is the derivative of x^2 is that the correct answer or is there anything else I should add? Thanks in advance
  2. jcsd
  3. Jan 28, 2006 #2


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    That would be okay enough, I guess.
  4. Jan 28, 2006 #3
    Well, x isn't the derivative of [itex]x^2[/itex], but I know what you meant. Maybe you could also show how basic substitution fails on the other two.
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