The sum of the inner angles of a triangle will always equal 180°.
The sum of the inner angles of any quadrilateral (with four sides) will always equal 360°.
The sum of interior angles of a regular or irregular polygon is equal to (n – 2) × 180°, where n is the number of sides in the polygon.
Angles on a straight line equal 180°.
Angles situated around a point equal 360°.
Vertically opposite angles that are formed with straight lines crossing will always be equal to each other.
Two angles are called supplementary if, when added together, they make 180°, regardless of whether they are adjacent or not.
Two angles are called complementary if, when added together, they make 90°, regardless of whether they are adjacent or not.
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