document.write( "Question 470192: Find the area of a rectangle with the vertices at (0,9) (0,-4) (5,-4) and (5,9) \n" ); document.write( "
Algebra.Com's Answer #322579 by Alan3354(69443)\"\" \"About 
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Find the area of a rectangle with the vertices at (0,9) (0,-4) (5,-4) and (5,9)
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\n" ); document.write( "it's 5 by 13
\n" ); document.write( "Area = 65
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\n" ); document.write( "Here's a general solution:
\n" ); document.write( "Label the points in order:\r
\n" ); document.write( "\n" ); document.write( "A(0,9) B(0,-4) C(5,-4) and D(5,9)
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\n" ); document.write( "A B C D A
\n" ); document.write( "0 0 5 5 0
\n" ); document.write( "9-4-4 9 9
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\n" ); document.write( "Add the diagonal products from the upper left:
\n" ); document.write( "0 + 0 + 45 + 45 = 90
\n" ); document.write( "Add the diagonal products from the lower left:
\n" ); document.write( "0 - 20 - 20 + 0 = -40
\n" ); document.write( "The difference is 130
\n" ); document.write( "The area is 1/2 that = 65 sq units.
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\n" ); document.write( "It works for all polygons, any number of sides.
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