Proof that The Diagonals of a Rhombus are Perpendicular

In the previous post, we have proved the converse of the Pythagorean Theorem.  In this post, we will prove that the diagonals of a rhombus are perpendicular to each other. That is, if we have parallelogram ABCD with diagonal and , then is perpendicular to . What We Know A rhombus is a parallelogram with four […]
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Quadrilaterals With Congruent Opposite Angles Are Parallelogram

In the previous post, we have proved that if the opposite sides of a quadrilateral are congruent, then they are parallel. In this post, we are going to show that if the opposite angles of a quadrilateral are congruent, then it is a parallelogram. In the figure below, we have quadrilateral ABCD with and . […]
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Proof that the Product of Two Rational Numbers is Rational

The purpose of this blog is to introduce mathematical proofs as early as possible. When I say mathematical proof, it does not have to be rigorous; sometimes simple reasoning by words alone would suffice especially in the early grades. In this post, I am going to show you a simple proof that can be probably […]
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