Regions in the plane

•A shape cut from paper is called a region in the plane. Some basic regions that you know about are triangles, squares, rectangles, and circles. Squares and rectangles are types of quadrilaterals (regions with four sides).

•Triangles and squares are examples of polygons. The word 'polygon' means 'many sides.' Here are the names for polygons with up to eight sides.


In the figure, click on the labeled boxes to see examples of quadrilaterals. A trapezoid is a quadrilateral in which two opposite sides are parallel, but the other two sides are not parallel.

In the lesson screens that follow, you will need to move the shapes around. Practice on the screen at the right. To slide a quadrilateral, click near the center and drag. To rotate it, click near a vertex (corner) and drag.