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Math Help - trig substitution

  1. #1
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    trig substitution

    suggest an appropriate trig substitution for x in

    int(x^5/(x^2-5)^3/2)dx
    and
    int((3-x^2)^5/2)dx
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  2. #2
    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by samdmansam View Post
    suggest an appropriate trig substitution for x in

    int(x^5/(x^2-5)^3/2)dx
    x = \sqrt{5} \sec \theta

    int((3-x^2)^5/2)dx
    x = \sqrt{3} \sin \theta
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  3. #3
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    The first one is also solvable by standard algebraic techniques.
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  4. #4
    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by Krizalid View Post
    The first one is also solvable by standard algebraic techniques.
    you mean a regular substitution of u = x^2 - 5, or something else?

    yes, that regular substitution will do it, but the poster asked for a trig substitution, so ...



    [off-topic]

    what happened to your other badge, Krizalid?

    [/off-topic]
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  5. #5
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    Yeah, but observe that I said "also."

    As for my another badge, I personally asked to be removed.
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  6. #6
    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by Krizalid View Post
    Yeah, but observe that I said "also."
    were you thinking about what i suggested, or something else?

    As for my another badge, I personally asked to be removed.
    really? how come? the badges getting too heavy?
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