Question 1010928
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Given: AB||DC
AD||BC
Prove: angle A and angle B are supplementary 
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Angle A and angle B are supplementary as they are interior angles on the same side at 
two parallel lines AD and BC and the transverse AB.


See the lesson &nbsp;<A HREF=http://www.algebra.com/algebra/homework/Angles/Parallel-lines.lesson>Parallel lines</A>&nbsp; in this site, &nbsp;<U>Parallel transversal theorem</U>.