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Thread: Finding the length of a diagonal

  1. January 30th 2010, 09:20 AM #1
    fmc123
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    Finding the length of a diagonal

    The width of a rectangle is 1 less than twice its length. If the area of the rectangle is 90 cm^2, what is the length of the diagonal?


    I know this has to do with the Pythagorean theorem, however, I just have not been able to figure out the answer. Help?
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  2. January 30th 2010, 09:25 AM #2
    e^(i*pi)
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    Quote Originally Posted by fmc123 View Post
    The width of a rectangle is 1 less than twice its length. If the area of the rectangle is 90 cm^2, what is the length of the diagonal?


    I know this has to do with the Pythagorean theorem, however, I just have not been able to figure out the answer. Help?
    A = \frac{1}{2}ab = 90

    a = 2b-1


    You can then use Pythagoras.

    d^2 = (2b-1)^2+b^2
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