Lines and Angles
- Acute angle: less than 90°
- Right angle: exactly 90°
- Obtuse angle: between 90° and 180°
- Straight angle: exactly 180°
- Reflex angle: between 180° and 360°
Angle Facts
- Angles on a straight line add up to 180°
- Angles at a point add up to 360°
- Vertically opposite angles are equal
- Alternate angles (Z-angles) are equal
- Co-interior angles add up to 180°
Triangles
The angles in any triangle add up to 180°.
| Type | Properties |
|---|---|
| Equilateral | All sides equal, all angles = 60° |
| Isosceles | Two sides equal, two base angles equal |
| Scalene | No sides equal, no angles equal |
| Right-angled | One angle = 90° |
Pythagoras Theorem
In a right-angled triangle: a² + b² = c² where c is the hypotenuse (longest side).
If a = 3 and b = 4: c² = 9 + 16 = 25, so c = 5