L2 Quadrilaterals
Completion requirements
Unit A: Geometry
Chapter 1: Polygons
Quadrilaterals
A quadrilateral has the following four properties:
- It has four sides.
- The sides join to form a closed shape.
- The interior angles add to 360°.
- The four corners lie flat on the same plane.
Diagonal: a line segment joining vertices in a polygon that are not next to each other.
Drawing diagonals in polygons was discussed in Lesson 1.
In a quadrilateral, the diagonal connects opposite vertices. Therefore, there are two diagonals in every quadrilateral.
In this quadrilateral, one diagonal in the quadrilateral is 10.5 cm and the other diagonal is 5 cm. Therefore, the diagonals are not equal. Each intersection of the diagonals forms a 90° angle. These angles are called diagonal angles.
Using the Quadrilateral applet, explore the properties of the special quadrilaterals.