Geometry Building BlocksA series of free High School Geometry Video Lessons from Brightstorm.
Angles: Types and Labeling There are four types of angles: acute, right, obtuse, and straight. Each name indicates a specific range of degree measurements. Congruent angles have equivalent measures. Adjacent angles share a vertex and a common side.
Using a Protractor In Geometry, it is important to know how to measure an angle. Using a protractor helps us determine the angle measurement so we can label it as acute, right or obtuse. Every protractor is a little bit different, but all will have a location on the bottom edge where we align the vertex of the angle we are measuring. After lining up the vertex, we line up the bottom edge of the protractor with one side of the angle and use the marks on the top to measure.
Angle Bisectors An angle is formed by two rays with a common endpoint. The angle bisector is a ray or line segment that bisects the angle, creating two congruent angles. To construct an angle bisector you need a compass and straightedge. Bisectors are very important in identifying corresponding parts of similar triangles and in solving proofs.
Supplementary and Complementary Angles Supplementary angles are two angles whose sum is 180 degrees while complementary angles are two angles whose sum is 90 degrees. Supplementary and complementary angles do not have to be adjacent (sharing a vertex and side, or next to), but they can be.
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