Question
Prove that a cyclic parallelogram is a rectangle.

Answer

Given,

ABCD is a cyclic parallelogram.

To prove,

ABCD is rectangle.

Proof:

$\angle1+\angle2=180^\circ$ (Opposite angles of a cyclic parallelogram)

also, Opposite angles of a cyclic parallelogram are equal.

Thus,

$\angle1=\angle2$

$\Rightarrow\angle1+\angle1=180^\circ$

$\Rightarrow\angle1=90^\circ$

One of the interior angle of the parallelogram is right angled. Thus, ABCD is a rectangle.

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