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Basic Geometry

Basic Geometry

At a Glance - Basic Shapes & Angles

This is where it all begins: basic shapes, lines, and angles.

Read on and let us take you on a magical geometry tour...

  • A single location.
  • Usually drawn as a dot.
  • It is "dimensionless".
  • Labeled as Point P. You used these when playing Connect the Dots.
Point P
  • A straight path passing through at least two points.
  • Extends in both directions forever.
  • Labeled as QR
  • Think of this as a highway that never ends.
Line QR
Line Segment
  • A portion of a line.
  • It has limits at each end.
  • Labeled as CD
  • You've drawn these since you were 1½!
Line segment CD
  • A straight path with one terminal point and extending indefinitely in the other direction.
  • Labeled as EFMake sure to start with the terminal point and extend past the other point.
  • Rays are an easy image. Picture the sun as a terminal point and its rays extending indefinitely into space.
Ray EF
  • A flat surface without boundaries.
  • Labeled by naming three nonlinear points on the plane, Plane GHI.
  • Planes are somewhat difficult to imagine. It's like a piece of paper that extends in every direction forever.
Plane GHI
Parallel Lines
  • Lines that lie on the same plane and never intersect.
  • Labeled as JK and LM
  • Look at a piece of lined paper. All the horizontal lines are parallel to each other.
Parallel Lines JK and LM
Perpendicular Lines
  • Lines that intersect at a 90° angle.
  • Labeled as NQ and PO
  • On that same lined paper the vertical margin lines are perpendicular to the horizontal ones.
Perpendicular Lines NQ and PO

Refer to the following diagram for the examples below


Plane Example

Two parallel lines

BD and CH

Exercise 1

What is the intersection of two unique, non-parallel lines?

Exercise 2

What is the intersection of two unique, non-parallel planes?

Exercise 3

How many dimensions does a plane have?