Types of Angles

There are different types of angles: An acute angle is between 0° and 90°

A right angle is 90°

Complementary angles are angles whose sum is 90°

An obtuse angle is between 90° and 180° A straight angle is 180°

Supplementary angles are angles whose sum is 180°

A reflex angle is between 180° and 360° An angle of revolution is 360° Angles at a point make up 360°

Coincidentally, vertically opposite angles are equal.

When a transversal cuts two lines, it forms pairs of angles. When the two lines are parallel, these pairs of angles have special properties. Corresponding angles are equal

They form an 'F' shape                                     These are vertically opposite angles Alternate angles are equal                                         Co-interior angles add up to 180°

They form a 'Z' shape                                                        They form a 'C' shape

Check out this Geogebra app that shows different situations of angles on parallel lines. Twig around it by using the slider to explore these angles (courtesy of Tim Brzezinski).