Question
Wed December 26, 2012 By:
 

if in a quadrilateral each pair of opposite sides are equal then proove that it a parallelogram

Expert Reply
Wed December 26, 2012
Let WXYZ be the quadrilateral.
We have:
angle W = angle Y
angle Z = angle X
 
Now, angle W + angle X + angle Y + angle Z = 360 degrees
angle W + angle Z = 180 degrees
 
But these are co-interior angles between lines WX and ZY. Therefore, WX || ZY.
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