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SpringBoard® Course 1 Math Skills Workshop Unit 5 • Getting Ready Practice
Two-Dimensional Figures
A plane is a flat surface that extends infinitely in all directions. A parallelogram like the one
below is often used to model a plane, but remember that a plane—unlike a parallelogram—has
no boundaries or sides.
A plane figure or two-dimensional figure is a figure that lies completely in one plane. When you
draw, either by hand or with a computer program, you draw two-dimensional figures. Blueprints
are two-dimensional models of real-life objects.
Polygons are closed, two-dimensional figures formed by three or more line segments that
intersect only at their endpoints. These figures are polygons.
These figures are not polygons.
This is not a polygon
because it is an open
figure.
A heart is not a polygon
because it is has curves. A circle is not a polygon
because it is made of
a curve.
Polygons are named by the number of sides and angles they have. A polygon always has the same
number of sides as angles. Listed on the next page are the most common polygons. Each of the
polygons shown is a regular polygon. All the angles of a regular polygon have the same measure
and all the sides are the same length.
MSW_C1_SE.indb 89 20/07/19 1:05 PM
