document.write( "Question 394928: State 5 ways to prove that a quadrilateral is a parallelogram? \n" ); document.write( "
Algebra.Com's Answer #280282 by Edwin McCravy(20065)\"\" \"About 
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document.write( "1. If both pairs of opposite sides of a quadrilateral are parallel, the\r\n" );
document.write( "quadrilateral is a parallelogram. (That's the definition of a parallelogram,\r\n" );
document.write( "the other 5 are theorems that can be proved.)\r\n" );
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document.write( "2. If both pairs of opposite sides of a quadrilateral are congruent, the\r\n" );
document.write( "quadrilateral is a parallelogram.\r\n" );
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document.write( "3. If one pair of opposite sides of a quadrilateral are both parallel and\r\n" );
document.write( "congruent, the quadrilateral is a parallelogram.\r\n" );
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document.write( "4. If the diagonals of a quadrilateral bisect each other, the quadrilateral\r\n" );
document.write( "is a parallelogram.\r\n" );
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document.write( "5. If both pairs of opposite angles of a quadrilateral are congruent, the\r\n" );
document.write( "quadrilateral is a parallelogram. \r\n" );
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document.write( "6. If every pair of adjacent angles of a quadrilateral are supplementary, the\r\n" );
document.write( "quadrilateral is a parallelogram.\r\n" );
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document.write( "Edwin
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