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Door 15 · Grade 3

📐 Points, Lines, Rays, Angles

Point = dot (no size)

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Point, Line Segment, Ray, and Angle

Geometry starts with basic building blocks:
• Point: An exact location in space (shown as a dot •)
• Line segment: A straight path with two endpoints (A________B)
• Ray: Starts at one endpoint and continues forever in one direction (→)
• Angle: Formed by two rays sharing the same endpoint (vertex)

Worked example

Problem: What geometry term describes the tip of a pencil?

  1. A point.
  2. A point marks an exact location with no size.

Answer: A point marks an exact location with no size.

Classify Angles: Right, Acute, Obtuse

Angles are classified by their size (measured in degrees °):
• Right angle: Exactly 90° — looks like a perfect corner (L shape)
• Acute angle: Less than 90° — smaller than a right angle (sharp, narrow)
• Obtuse angle: More than 90° — larger than a right angle (wide, blunt)

A small square symbol in the corner means it is a right angle.

Worked example

Problem: What angle is at the corner of a square?

  1. A right angle (90°).
  2. All four corners of a square are right angles.

Answer: All four corners of a square are right angles.