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    • Thread Starter

    Hi, I'm really stuck on some homework, it involves an integral i must solve by t-substitution. I was on the wikipedia page for this:
    But i can't for the life of me work out how they substituted the dx in this part:

    This of course comes from:

    and I understand therefore why sinx has been substituted but why is dx = 2dt/1+t^2? (shown last on the identity list) Is it just something we're expected to learn and know?
    • Thread Starter

    Don't worry, I worked it out, for all concerned:
    dt/dx = (1/2)sec^2(x/2)
    dt = (1/2)(1+t^2)dx
    dx = 2dt/(1+t^2)
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Updated: October 30, 2015
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