📐 Lines and Angles

In geometry, a line is a straight path. In Grade 4, we study three important relationships between lines:
• Parallel Lines: Lines that never meet and are always the same distance apart. Like railway tracks or opposite edges of a ruler.
• Perpendicular Lines: Lines that meet at exactly 90 degrees (a right angle). Like the corner of a room or the letter L.
• Intersecting Lines: Lines that cross each other at any angle. Like scissors or roads crossing at a junction.

A line segment has two endpoints. A ray has one endpoint and goes on forever in one direction.

An angle is formed when two rays meet at a common point called the vertex. Angles are measured in degrees (°).
Three main types of angles:
• Acute Angle: Less than 90 degrees (sharp, like the tip of a pencil)
• Right Angle: Exactly 90 degrees (like the corner of a square)
• Obtuse Angle: Between 90 and 180 degrees (wider than a right angle)

A straight angle = 180 degrees (a straight line).

A protractor is the tool used to measure angles in degrees.
Steps to measure an angle with a protractor:
• Place the centre hole of the protractor at the vertex of the angle
• Align the baseline (0 line) with one ray of the angle
• Read the degrees where the second ray crosses the scale
• Use the scale that starts from 0 on the side where you placed the baseline

Protractors have two scales — always use the correct one!