Types of Angles (Mathematics Lesson)
Types of AnglesAngles can be classified as acute, right, obtuse, straight, reflex or full.
Acute AnglesAn acute angle is an angle of less than 90°.
Read more about acute angles
Right AnglesA right angle is an angle of 90°.
(Note: Right angles are often denoted by adding a small right angle that forms a square with the angle.)
Read more about right angles
Obtuse AnglesAn obtuse angle is an angle greater than 90° and less than 180°.
Read more about obtuse angles
Straight AnglesA straight angle is an angle of 180°.
Read more about straight angles
Reflex AnglesA reflex angle is an angle greater then 180° and less than 360°.
Read more about reflex angles
Full AnglesA full angle is an angle of 360°.
Read more about full angles
NoteWHAT 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".