Definitions and properties of angles in geometry.

## An Angle in GeometryAn angle is the rotation required to superimpose one of two intersecting lines on the other.
## Right AngleA right angle is an angle with measure equal to 90 degrees.
## Straight AngleA straight angle is an angle with measure equal to 180 degrees.
## An Acute AngleAn acute angle is an angle with a measure between 0 and 90 degrees.
## An Obtuse AngleAn obtuse angle is an angle with a measure between 90 and 180 degrees.
## Complementary AnglesTwo angles are complementary if the sum of their measures is equal to 90 degree.Example: angles a and b with measures a = 19° and b = 71° are complementary since a + b = 90°
## Supplementary AnglesTwo angles are supplementary if the sum of their measures is equal to 180 degrees.Example: angles a and b with measures a = 122.1° and b = 57.9° are supplementary since a + b = 180°
## Exercises (see solutions below)Given angles a, b, c, d, e and f with measuresa = 21° b = 90.1° c = 90° d = 134.2° e = 69° f = 45.8° 1 ) Which of these angles are acute? 2 ) Which of these angles are obtuse? 3 ) Which pairs of angles are complementary? 4 ) Which pairs of angles are supplementary?
## Solutions to Above Exercises1 ) a, e and f 2 ) b and d. 3 ) a - e 4 ) d - f ## More References and Links to Geometry TutorialsQuestions on Angles with Solutions and ExplanationsGeometry Tutorials and Problems |