November 10, 2008

This resource has been contributed by Winpossible, and can also be accessed on their website by clicking here - Properties of Quadrilaterals.

Here you'll learn the important properties of quadrilaterals and how to apply the correct property to each different type of quadrilateral. The interactive learning of lessons and practice questions with solution, is presented by instructor with the help of video of their voice and own handwriting.

The three properties that we are going to look at are - the number of sides, interior angles (the angles inside) and the length of the sides. A quadrilateral is a polygon with four sides and it has four vertices. You'll have explanation; with the help of examples including solution, of the adjacent sides, opposite sides, adjacent angles or consecutive angles and opposite angles of a quadrilateral.

Two sides of a quadrilateral, which have a common vertex, are called adjacent sides E.g. in quadrilateral *ABCD*, *AB* and *BC*, *BC* and *CD*, *CD* and *DA*, *DA* and *AB* are the pairs of adjacent sides. Two sides of a quadrilateral are opposite, if they do not have a common endpoint i.e. *AB* and *DC*, *BC* and *AD* are two pairs of opposite sides.

Two angles of a quadrilateral having rays on the same line are known as adjacent angles or consecutive angles i.e. *A* and *B*, *B* and *C*, *C* and *D*, *D* and *A* are the pairs of adjacent angles. Two angles of a quadrilateral that do not have rays on the same line are known as opposite angles E.g. *A* and *C*, *B* and *D*, are pairs of opposite angles.

In quadrilateral *ABCD*, diagonal *AC* divides quadrilateral into two triangles ?*ABC* and ?*ADC*. We know from earlier learnings that sum of the interior angles of a triangle is 180°; therefore, sum of the interior angles of a quadrilateral is 180° + 180° = 360°. If the measurements of three angles of a quadrilateral are known, then the missing angle can be calculated. For example, in a quadrilateral *ABCD*, *ABC* is a right angle, *BCD* = 70° and *BAD* = 100°, then measure of *ADC* equals to 100°.

This FREE mini-lesson is a part of Winpossible's online course that covers all topics within Geometry. Click on the video below to go through it. If you like it, you can buy our online course in Geometry by clicking here.

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