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Math Help - Ellipse's

  1. #1
    N736RA_UMO
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    Ellipse's

    Use the parametric equations of an ellipse:
    x=7cos(theta)
    y=22sin(theta)
    0<theta<2pi (those are less than or equal to).
    to find the area that it encloses.
    Any help would be appreciated, thanks in advance!
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  2. #2
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    Area of Ellipse

    The polar coordinates describe an ellipse with a major axis along the y-axis and a minor axis along the x-axis. If you look at the equations, you can see that x reaches its maximum value, 7, when cos(theta)=1, which occurs at theta=0 and 2pi. Likewise, x reaches its minimum value, -7, when cos(theta)=-1, which occurs at theta=pi.

    You can perform the same analysis for y, using the values for theta for which sin(theta) reaches its maximum and minimum values, to determine the maximum and minimum values for y.

    The minor axis has a length of 14, since it stretches from x=-7 to x=7.

    You should be able to find the length of the major axis by determining the max and min values for y.

    The formula for the area of an ellipse is (pi)(A)(B) where A and B represent the lengths of the SEMI-major and SEMI-minor axes. Note that the SEMI-major axis is half the length of the major axis; the SEMI-minor and minor axes have a similar relationship.

    Todd Werner
    Director, Mathnasium West LA
    Math Tutoring at Mathnasium Math Learning Centers
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