Angles

Types of Angles

Name	Size
Acute	0° < x < 90°
Right	exactly 90°
Obtuse	90° < x < 180°
Straight	exactly 180°
Reflex	180° < x < 360°

Key Angle Rules

Angles on a straight line = 180°

Angles around a point = 360°

Vertically opposite angles are equal (formed where two lines cross)

Angles in a triangle = 180°

Angles in a quadrilateral = 360°

Interior angles of a regular polygon: Sum = (n - 2) × 180°, where n = number of sides

Angles and Parallel Lines

When a transversal crosses two parallel lines:

• Corresponding angles (F-shape) are equal
• Alternate angles (Z-shape) are equal
• Co-interior angles (C-shape) add up to 180°

Example

A triangle has angles 47° and 63°: Third angle = 180° - 47° - 63° = 70°

Bearings

Bearings are angles measured clockwise from North, written as three digits:

• North = 000°, East = 090°, South = 180°, West = 270°