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Math Help - Parametric Equations to Rectangular Equation

  1. #1
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    Parametric Equations to Rectangular Equation

    Find the rectangular equation of the curve:
    the parametric curve x = 2 sin(t), y = 2 cos(t).

    I know it is a circle, centered at the origin, with radius of 2. But, since it goes clockwise, instead of counterclockwise like circles normally do, I can't figure out the rectangular equation.
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  2. #2
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    Quote Originally Posted by kiddopop View Post
    Find the rectangular equation of the curve:
    the parametric curve x = 2 sin(t), y = 2 cos(t).

    I know it is a circle, centered at the origin, with radius of 2. But, since it goes clockwise, instead of counterclockwise like circles normally do, I can't figure out the rectangular equation.
    square both equations ...

    x^2 = 4\sin^2{t}

    y^2 = 4\cos^2{t}

    -------------------- add em' up

    x^2 + y^2 = \, ?
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  3. #3
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    x^2 + y^2 = 4 sin^2(t) + 4 cos^2(t)? How is that right? I thought that when you change parametric equations to a rectangular equation you get rid of the "t's."
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  4. #4
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    Quote Originally Posted by kiddopop View Post
    x^2 + y^2 = 4 sin^2(t) + 4 cos^2(t)? How is that right? I thought that when you change parametric equations to a rectangular equation you get rid of the "t's."
    you did not finish it ...

    what does 4\sin^2{t} + 4\cos^2{t} = 4(\sin^2{t}+\cos^2{t}) = \,?
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  5. #5
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    Ohhhhh. I didn't even think of that. Sorry. Thanks for the help!
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