Angles: a figures is made by two rays (its sides), having one common closing point called its vertex, on a plane. Angles are used to measure the turn movement.
Types of angle: Acute angle, Right angle, Obtuse angle, Straight angle, Reflex angle.
Acute angle is an angle that is less than 90°.
Right angle is an angle that is equal to 90°.
Obtuse angle is an angle greater than 90°.
Straight angle is an angle equals to 180°.
Reflex angle is an angle greater than 180°.