Properties of Rectangles | ||
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Introduction | ||
This lesson page will inform you about the properties of rectangles. Here are the sections within this lesson page:
Before reading on with the sections in this lesson, we recommend that you first review this lesson:
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A rectangle is an equiangular parallelogram. Since a rectangle is a parallelogram and a parallelogram is a quadrilateral, a rectangle has all of the properties of both a parallelogram and a quadrilateral in addition to being equiangular.
The sections below will address the properties that are unique to rectangles.
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If the internal angles are equiangular, they are congruent (by definition of equiangular). We know that the internal angles of a quadrilateral have a sum of 360 degrees (see Properties of Quadrilaterals, Property: Internal Angles). Since the angles are congruent, they must all be equal to 90 degrees.
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Four Right Angles | |
Here is rectangle ABCD with diagonals AC and BD.
![]() There are numerous triangle in the diagram. However, we will focus on two overlapping triangles, triangles ADC and BCD. Opposite sides are congruent for parallelograms; so, segment AD is congruent segment BC. Segment DC is congruent to itself by the reflexive property. In the last section (Properties: Internal Angles), we found that all the angles are 90 degrees. If we pull out the triangles from the diagrams and their congruent attributes, this is what we see.
![]() Triangle ADC is congruent to triangle BCD by SAS. By CPCTC, segment AC is congruent to segment BD. This means...
Rectangle are Congruent | |
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