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Terms + Definitions : Angles Angle
- An angle is created by two rays that share an endpoint (for more on
rays, see basic geometry terms.) Vertex
of an Angle - The point where the angle's two rays
intersect. Sides
of an Angle - The two rays that form the angle. Acute
Angles -An angle measuring between 0 and 90 degrees. Obtuse
Angles - An angle measuring between 90 and 180 degrees. Right
Angles - 90 degree angles. Complementary
Angles - If the sum of the degrees of two angles equals 90 degrees
then the two angles are referred to as complementary. Supplementary
Angles - If the sum of the degrees of two angles equals 180 degrees
then the two angles are referred to as supplementary. Vertical
Angles - Two angles whose sides from two pairs of opposite
rays. Interior
Angles - Angles lying on the interior, or "inside", of a set
of lines or figure. Alternate
Interior Angles - When a pair of parallel lines is intersected by a
third line, congruent angles (angles of the same size) are formed on each
parallel line. That is, the four angles on parallel line A will be
the same as on parallel line B. Alternate Interior Angles are
interior angles ("inside" angles) that lie on different parallel
lines and on opposite sides of a transversal (see basic
geometry terms for a definition of transversal). Alternate
Exterior Angles - When a pair of parallel lines is intersected by a
third line, congruent angles (angles of the same size) are formed on each
parallel line. That is, the four angles on parallel line A will be
the same as on parallel line B. Alternate Exterior angles are
exterior angles ("outside" angles) that line on different
parallel lines and on opposite sides of a transversal (see basic
geometry terms for a definition of transversal). Corresponding
Angles - Angles that are in the same location relative to the nearest
parallel line. Bisector
- A ray that divides an angle into two separate angles. Perpendicular
Lines - Two lines that meet to form a right angle are referred to
as perpendicular lines.
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