Angles

An angle is a measure of turn — it tells us how far one line has rotated from another around a shared point. Angles are measured in degrees (°), with a full turn being 360° and a half turn being 180°. There are several types of angle. An acute angle is less than 90°. A right angle is exactly 90° — the corner of a square — and is marked with a small square symbol. An obtuse angle is greater than 90° but less than 180°. A straight angle is exactly 180° (a straight line). A reflex angle is greater than 180°. Knowing angle facts helps us calculate unknown angles: angles on a straight line add up to 180°; angles around a full point add up to 360°; and angles in a triangle always add up to 180°. We measure angles using a protractor, aligning its centre point with the vertex (corner) of the angle and reading the scale. Angles appear in architecture, engineering, sport, navigation and art.