Chapter One
Introduction to
Two-Dimensional (2-D)
Geometric Figures
Two-dimensional geometry, coordinate plane geometry, Cartesian
geometry, and planar (pronounced PLANE-er) geometry refer to the
same thing: the study of geometric forms in the coordinate plane. Do
you remember the coordinate plane? It's a grid system in which two
numbers tell you the location of a point-the first, x, tells you how far
left or right to go from the origin (the center point), and the second
number, y, tells you how far up or down to go. The y-axis is vertical
and the x-axis is
horizontal (like
the horizon).
You'll see a lot more of the coordinate
plane in geometry, but
sometimes all that matters is knowing
that a figure is in the plane or
two-dimensional without knowing
a precise address for it. This part
will introduce you to some of the
most common figures in two-dimensional
geometry and give
you some names for their parts and
ways to work with them.
In this part, Dr. Math explains
points, lines, and planes
angles
triangles
quadrilaterals
1 Points, Lines, and Planes
... read full excerpt from Dr. Math Gets You Ready for Geometry: Learning Geometry Is Easy! Just Ask Dr. Math! ebook
