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Basic Geometry

Basic Geometry

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

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


NameDescriptionExample
Point
  • 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
Line
  • 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
Ray
  • 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
Plane
  • 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

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