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document.write( "Given: Trapezoid ABCD, \r\n" );
document.write( " AC = DB\r\n" );
document.write( "To prove: AB = DC\r\n" );
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document.write( "AD ∥ BC definition of a trapezoid\r\n" );
document.write( "∠DAC = ∠BCA, ∠ADB = ∠DBC alternate interior angles\r\n" );
document.write( "ΔADE ∽ ΔCBE two angles equal in each \r\n" );
document.write( "AE/EC = DE/EB corresponding sides of similar \r\n" );
document.write( " triangles are proportional\r\n" );
document.write( "AE/EC+1 = DE/EB+1 adding the same quantity, 1, to both sides\r\n" );
document.write( "AE/EC+EC/EC = DE/EB+EB/EB replacing 1 by EC/EC and by EB/EB\r\n" );
document.write( "(AE+EC)/EC = (DE+EB)/EB adding fractions \r\n" );
document.write( "AE+EC = AC, DE+EB = DB a whole is the sum of its parts \r\n" );
document.write( "AC/EC = DB/EB Substitution of equals for equals\r\n" );
document.write( "AC = DB Given\r\n" );
document.write( "AC/EC = AC/EB Substitution of equals for equals\r\n" );
document.write( "AC*EB = AC*EC Cross-multiplication or product of\r\n" );
document.write( " extremes equal product of means.\r\n" );
document.write( "EB = EC Dividing both sides by AC \r\n" );
document.write( "ΔEBC is isosceles two sides equal\r\n" );
document.write( "∠ECB = ∠EBC base angles of an isosceles triangle\r\n" );
document.write( "AC = DB given\r\n" );
document.write( "BC = BC identity\r\n" );
document.write( "∠ACB = ∠DBC Same as ∠ECB = ∠EBC \r\n" );
document.write( "ΔABC ≅ ΔDCB SAS \r\n" );
document.write( "AB = DC Corresponding parts of congruent triangles\r\n" );
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document.write( "Edwin
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