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Math Help - Need to find Inverse of...

  1. #1
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    Need to find Inverse of...

    Can anyone help me out for finding the inverse of this function? I'm not quite sure how to find the inverse of a polynomial...

    y=2x^3+3x^2+7x+4

    Thank you!

    Also if you can help me find this integral...


    <br />
\int_0^{\frac{\pi}{4}}\tan^2{x} dx<br />
    Last edited by yamuda; April 20th 2008 at 01:18 PM.
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  2. #2
    MHF Contributor Mathstud28's Avatar
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    Quote Originally Posted by yamuda View Post
    Can anyone help me out for finding the inverse of this function? I'm not quite sure how to find the inverse of a polynomial...

    y=2x^3+3x^2+7x+4

    Thank you!

    Also if you can help me find this integral...


    <br />
\int_0^{\frac{\pi}{4}}\tan^2{x} dx<br />
    For the first one swith x's and y's and solve for y again.

    second one \int_0^{\frac{\pi}{4}}tan^2(x)dx=\int_0^{\frac{\pi  }{4}}[sec^2(x)-1]dx=tan(x)-x\bigg|_0^{\frac{\pi}{4}}=1-\frac{1}{4}\pi
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  3. #3
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    Quote Originally Posted by Mathstud28 View Post
    For the first one swith x's and y's and solve for y again.

    second one \int_0^{\frac{\pi}{4}}tan^2(x)dx=\int_0^{\frac{\pi  }{4}}[sec^2(x)-1]dx=tan(x)-x\bigg|_0^{\frac{\pi}{4}}=1-\frac{1}{4}\pi
    mmm thanks a lot, but im having trouble with the inverse, i know how to do inverse, but im not sure what to do with this polynomial....
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  4. #4
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    Quote Originally Posted by yamuda View Post
    Can anyone help me out for finding the inverse of this function? I'm not quite sure how to find the inverse of a polynomial...

    y=2x^3+3x^2+7x+4

    Thank you!
    [snip]
    Unless you can write it in the form y = a(x - h)^3 + k (which you can't - there's a point of inflexion at (-1/2, 1) but it's not a stationary point of inflexion) you'll have to solve x = 2y^3 + 3y^2 + 7y + 4 for y using Cardano's method (see Cubic function - Wikipedia, the free encyclopedia)
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