Classifying Quadrilaterals
Do you know the answers to the above properties? Don't worry if you don't, because this page will cover everything about quadrilaterals and their properties. But if you want to know the answers, here they are:
(Parallel, equal, angles, 90º, opposite, sides, equal, bisect, sides, opposite, parallel, opposite, equal, right, bisect, equal, parallel, 90º, equal, bisect, equal, 90º, sides, equal, 90º)
Classifying quadrilaterals is easy. Just find out what properties the shape has, then decide what geometrical figure it matches. The shapes don't have to look the same, so it's really important to know all properties of quadrilaterals. Below are two easy ways, called quadrilateral family trees, to remember:
(Parallel, equal, angles, 90º, opposite, sides, equal, bisect, sides, opposite, parallel, opposite, equal, right, bisect, equal, parallel, 90º, equal, bisect, equal, 90º, sides, equal, 90º)
Classifying quadrilaterals is easy. Just find out what properties the shape has, then decide what geometrical figure it matches. The shapes don't have to look the same, so it's really important to know all properties of quadrilaterals. Below are two easy ways, called quadrilateral family trees, to remember:
The angle sum of a quadrilateral
In quadrilaterals, the angle sum is always 360º. Prove it to yourself by following the instructions above.
Below is how to find the unknown angle in a quadrilateral, and it's very similar to finding the unknown angle in a triangle, except with one more angle.
Below is how to find the unknown angle in a quadrilateral, and it's very similar to finding the unknown angle in a triangle, except with one more angle.
First, add up all the known angles, then subtract that number by 360º. Again, this is a very simple equation to solve. Just don't get quadrilaterals and polygons mixed up. Quadrilaterals have four sides, like a rectangle or a square. Polygons have many sides, and can include a hexagon and octagon. These figures have completely different angle sums. The examples below will explain more about this.
Angle sum of a convex polygon
The formula for finding the angle sum of a convex polygon is shown above. This will be used in the activity section of this website, so revise it well. Divide the polygon into as many triangles as you can, then multiply that number by 180. This will give you the angle sum of the figure, for example, a hexagon can be divided into 4 triangles. 4 x 180 = 720. This is the angle sum of all hexagons. The formula A=180(n-2) is another quicker method of finding the angle sum of a polygon.