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W.1 Points, lines, line segments, rays, and angles

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What is a Point?

A point names an exact location in space. It has no length, width, or thickness.

Example:
  • A point is usually named with a capital letter, like Point A.
  • Written as: A
Note

Think of a point as a dot that shows a position. It is the building block of geometry.

What is a Line?

A line is a straight path that goes on forever in both directions. It has no endpoints.

Example:
  • A line through points A and B is written as: AB
  • It never stops.
Note

A line always extends in both directions without ending. You cannot measure its length.

What is a Line Segment?

A line segment is part of a line. It has two endpoints and a fixed length.

Example:
  • A line segment from point A to point B is written as: AB
  • Unlike a line, it can be measured.
Note

Remember: a line segment has a beginning and an end. It does not go on forever.

What is a Ray?

A ray is part of a line. It has one endpoint and extends forever in one direction.

Example:
  • A ray starting at point A and passing through point B is written as: AB
  • A is the endpoint, and the ray extends through B and beyond.
Note

A ray always begins at a point and goes on without end in one direction.

What is an Angle?

An angle is formed when two rays share the same endpoint, called the vertex.

Example:
  • If ray BA and ray BC share endpoint B, they form an angle.
  • Written as ∠ABC (vertex in the middle).
Note

Angles can be described as right, acute, or obtuse depending on their size. Always name the angle using three points with the vertex in the middle.