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Math Help - double integral

  1. #1
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    double integral

    can someone help me with this double integral please.

    DOUBLE INTEGRAL: e^-r^2 r dr dtheta
    where r is bounded by 0 and a
    and theta is bounded by 0 and pi/2

    thanks
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  2. #2
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    Hello, mesterpa!

    It seems to be easy enough . . .


    Can someone help me with this double integral please.

    ∫∫ e^{-r} r dr dθ

    . . where r is bounded by 0 and a
    . . and θ is bounded by 0 and π/2

    The inner integral is: .
    e^{-r} r dr

    Let: u = -r . . du = -2r dr

    And we have: .-
    e^u du .= .- e^u . . -e^{-r}

    Now evaluate for r = 0 to r = a.


    Then integrate with respect to θ and evaluate.

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  3. #3
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    hi. thanks for your help.
    sorry my experience of integration is very little.
    could you tell me which method if integration this is being used.
    thanks
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