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Cartesian Equations

  1. Jul 14, 2012 #1

    knv

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    1. Find a Cartesian equation to represent the curve r = 9 cosθ



    2. I know that rcosθ= x and cos θ= x/r



    3. I got (x-9/2)^2 +y^2 = (9/2)^2 but its coming up wrong when I put it into our online homework. Can anyone help me?
     
  2. jcsd
  3. Jul 14, 2012 #2

    tiny-tim

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    hi knv! :smile:

    (try using the X2 button just above the Reply box :wink:)
    how?? :confused:

    anyway, just multiply by r …

    r2 = 9rcosθ :smile:
     
  4. Jul 14, 2012 #3

    LCKurtz

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    Your result looks correct to me. It probably has something to do with how you "simplify" it before you type in the answer. Maybe something simple like writing the right side as 81/4?
     
  5. Jul 14, 2012 #4

    knv

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    the answer was more simple than I thought.

    x2+y2=9x


    Thanks!
     
  6. Jul 14, 2012 #5

    LCKurtz

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    So your original answer was correct, just not in the form the software wanted.
     
  7. Jul 14, 2012 #6

    knv

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    yes. I always get things wrong just because its not in the form the software wanted. Miss when we could turn homework in on paper haha
     
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