Lines & Angles
Year 7 📐 Geometry & Measures Measure angles, identify angle types and use angle properties.
📐 Types of Angles
Angles are measured in degrees (°). Knowing angle types is essential for geometry.
| Type | Size |
|---|---|
| Acute | Less than 90° |
| Right angle | Exactly 90° |
| Obtuse | Between 90° and 180° |
| Straight | Exactly 180° |
| Reflex | Between 180° and 360° |
↔️ Angle Relationships
Several key rules link angles formed by lines.
⚡ Key Rules
- Angles on a straight line sum to 180°
- Angles around a point sum to 360°
- Vertically opposite angles are equal
Example: Two angles on a straight line are $3x$ and $x + 20$. So $3x + x + 20 = 180$ → $4x = 160$ → $x = 40$, giving angles 120° and 60°.
🔀 Parallel Lines
When a transversal crosses two parallel lines, special angle pairs are formed.
- Alternate angles (Z-angles): equal
- Co-interior angles (C-angles): add to 180°
- Corresponding angles (F-angles): equal
Mark parallel lines with arrows on diagrams and always state the angle rule you are using in your working.
Ready to test yourself? Click the Quiz tab above to answer questions on this topic!
Interactive Demonstration — Lines & Angles
📐 Angle Calculator