Angles

• An angle is formed by two rays with a common end point


• The common point becomes the vertex of the angle


• Angles can be measured in degrees


• You can use a protractor to measure angles

Acute angles have a measure less than 90 degrees Angle ABC is an acute angle



Right angles have a measure equal to 90 degrees Angle ABC is a right angle
You can mark a right angle by placing a box at the vertex of the angle




Obtuse angles have a measure greater than 90 degrees and less than 180 degrees Angle DEF is an obtuse angle



A straight angle is a straight line
A straight angle has a measure equal to 180 degrees
Angle JKL is a straight angle



Angles are complementary angles when the sum of the measures of two angles is 90 degrees
ÐABD and ÐDBC and complementary angles




Angles are supplementary angles when the sum of the measures of two angles is 180 degrees
ÐAOD and ÐDOC are supplementary angles



Vertical angles are formed when two lines intersect
Ðs a and b and angles c and d are pairs of vertical angles