# Geometry Ch. 4 Terms

Term Definition
Acute Triangle A triangle in which all of the angles are acute angles.
Auxiliary Line An extra line or segment drawn in a figure to help complete a proof.
Base Angles The two angles formed by the base and the congruent sides
Congruence Transformation A mapping for which a geometric figure and its image are congruent.
Congruent Polygons Polygons in which all matching parts are congruent.
Coordinate Proof Proofs that use figures in the coordinate plane and algebra to prove geometric concepts.
Corollary A statement that can be easily proved using theorem is called a corollary of that theorem.
Corresponding Parts Matching parts of congruent polygons.
Equiangular Triangle A triangle with all angles congruent.
Equilateral Triangle A triangle with all sides congruent.
Exterior Angle An angle formed by one side of a triangle and the extension of another side.
Flow Proof A proof that organizes statements in logical order, starting with the given statements.
Included Angle In a triangle, the angle formed by two sides is the included angles for those two sides.
Included Side The side of a polygon that is a side of each two angles.
Isosceles Triangle A triangle with at least two sides that are congruent.
Obtuse Triangle A triangle with an obtuse angle.
Reflection A transformation representing the flip of a figure over a point, line or plane.
Remote Interior Angles The angles of a triangle that are not adjacent to a given exterior angle.
Right Triangle A triangle with a right angle.
Rotation A transformation that turns every point of a preimage through a specified angle and angle and direction about a fixed point or center of rotation.
Scalene Triangle A triangle with no two sides congruent.
Translation A transformation that moves a figure the same distance in the same direction.
Vertex Angle The angle with sides that are the legs