Question

Prove that every rectangle is a parallelogram.

Answer 1

Given : PQRS is a rectangle.

$\angle$P = $\angle$R = 90${}^{\circ }$

$\angle$Q = $\angle$S = 90${}^{\circ }$

Here opposite angles of the quadrilateral are congruent.

A quadrilateral is a parallelogram if its pairs of opposite angles are congruent. Hence rectangle PQRS is a parallelogram.