# Angles in Geometry

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.
## 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 ^{o} and b = 71^{o} are complementary since a + b = 90^{o}
## 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 ^{o} and b = 57.9^{o} are supplementary since a + b = 180^{o}
## Exercises (see solutions below)Given angles a, b, c, d, e and f with measuresa = 21 ^{o}b = 90.1 ^{o}c = 90 ^{o}d = 134.2 ^{o}e = 69 ^{o}f = 45.8 ^{o}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 TutorialsGeometry Tutorials, Problems and Interactive Applets. |