Types of Angles (Mathematics Lesson)
Types of Angles
There are different types of angle.
Angles can be:
An acute angle is an angle of less than 90°.
A right angle is an angle of 90°.
Don't forget: Right angles are often denoted by adding a small right angle that forms a square with the angle.
An obtuse angle is an angle greater than 90° and less than 180°.
A straight angle is an angle of 180°.
A reflex angle is an angle greater then 180° and less than 360°.
A full angle is an angle of 360°.
What Is an Angle?
An angle is created by two rays that have a common end point, called the vertex.
Who Classified Angles?
Euclid classified angles in his book, Elements.
Definition 10: "When a straight line standing on a straight line makes the adjacent angles equal to one another, each of the equal angles is right".
Definition 11: "An obtuse angle is an angle greater than a right angle".
Definition 12: "An acute angle is an angle less than a right angle".
Acute and obtuse angles are also oblique angles. Oblique angles are neither right angles nor multiples of right angles.