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 |
