ABCD be a parallelogram. Let O be the point of intersection of its diagonals
if < ABC = < COD
proof that ABCD be asqure
identify the two acute angles at B as a and b. < COD =<a +b given.label all angles of the figure in terms of a,b,c using the equality of coresponding angles.you can show the angles of triangle AOB add up to 2a+2b=180 so a+b=90
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