Q4 of 23 Page 274

If a parallelogram is cyclic, then it is a rectangle. Justify.

Let ABCD be a cyclic parallelogram.


A rectangle is a parallelogram with one angle 90. So, we have to prove angle 90.


Since ABCD is a parallelogram,


∠A = ∠C


In cyclic parallelogram ABCD,


∠A + ∠C = 180


∠A + ∠A = 180


2∠A = 180


∠A =


∠A = 90


Hence, proved.


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