document.write( "Question 1137368: is this quadrilateral, with the given vertices, a rectangle, by using coordinate
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Algebra.Com's Answer #755281 by Edwin McCravy(20055)\"\" \"About 
You can put this solution on YOUR website!
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document.write( "First let's draw it on graph paper to see what we think it is:\r\n" );
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document.write( "It looks like a rectangle. To prove that it is a rectangle by coordinate\r\n" );
document.write( "geometry, show that it is a parallelogram with one right interior angle:\r\n" );
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document.write( "1. Use the slope formula to find the slopes of all four sides.\r\n" );
document.write( "2. Show that both pairs of opposite sides have the same slope.\r\n" );
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document.write( "That's enough to show that it is a parallelogram.\r\n" );
document.write( "Then, to show that it is has one right angle, show that any one pair\r\n" );
document.write( "of adjacent sides have slopes which are negative reciprocals of each other.\r\n" );
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document.write( "(If a parallelogram has one right angle, then the other three are\r\n" );
document.write( "automatically right angles, too.)\r\n" );
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document.write( "Edwin
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