Angle Information Topic Index | Geometry Index | Regents Exam Prep Center

An
angle  is the intersection of two rays with a common endpoint

 Remember that an angle is named using three letters, where the middle letter corresponds to the vertex of the angle.  The angle at the right is
 If D lies in the interior of

 Types of Angles  (Definitions)

An acute angle is an angle whose measure is less than 90°

A right angle is an angle whose measure is 90°.

 An obtuse angle is an angle whose measure is more than 90°,                             but less than 1800

A straight angle is an angle whose measure is 180°.

A reflex angle is an angle whose measure is more than 180°.

 Pairs of Angles (Definitions)

The definitions above apply to angles when we look at one angle alone, but there are also some special relationships between pairs of angles.

 Adjacent Angles are 2 angles that share a common vertex, a common side and no common interior points.                       (They share a vertex and share a side, but do not overlap.) <1 and <2 are adjacent angles. <1 and
 THEOREM:  Supplements of the same angle, or congruent angles, are congruent.   A Linear Pair is 2 adjacent angles whose non-common sides form opposite rays. The angles MUST be adjacent. <1 and <2 form a linear pair. The line passing through points A, B, and C is a straight line. <1 and <2 are supplementary.

THEOREM:  If two angles form a linear pair, they are supplementary.

THEOREM:  If two congruent angles form a linear pair, they are right angles.

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