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Ch4 Vocabulary

Triangle Vocabulary

Acute Triangle A triangle where ALL angles are acute (less than 90 degrees)
Obtuse Triangle A triangle where one angle is obtuse (greater than 90 degrees but less than 180 degrees)
Right Triangle A triangle where one angle is right (EQUAL to 90 degrees)
Equilateral Triangle A triangle where all sides are congruent
Scalene Triangle A triangle where all three sides have different lengths
Isosceles Triangle A triangle with two sides congruent
Base Angles the two angles of an isosceles triangle formed by the base and one of the congruent sides (‘bottom angles’)
Vertex Angle the angle of an isosceles triangle formed by the congruent sides (‘top angle’)
Isosceles Triangle Theorem If two sides of a triangle are congruent, then the triangle is isosceles
Angle Sum Theorem (aka Triangle Theorem) The sum of the measures of the interior angles of a triangle is 180 degrees
Exterior Angle The angle formed outside of the triangle by extending one side of the triangle out of the triangle
Remote Interior Angles The two interior angles of the triangle NOT ADJACENT (next to) the given exterior angle referenced
Exterior Angle Theorem The measure of an exterior angle of a triangle is equal to the sum of the measures of the two remote interior angles
Flow Proof A proof that organizes a series of statements in a logical order starting with given statements. Each statement following includes a reason verifying the statement
Corollary 4.1 The acute angles of a right triangle are complementary (their sum is 90 degrees)
Congruent Triangles Triangles that are the same size and shape
CPCTC Two triangles are congruent if and only if (IFF) their corresponding parts are congruent – Corresponding Parts of Congruent Triangles are Congruent
Congruence Transformation to slide, flip or turn a triangle and the size or shape doesn't change
Included Angle The angle of a triangle BETWEEN the two given sides of the same triangle
Included Side The side of a triangle BETWEEN the two given angles of the same triangle
Corollary 4.4 (Equilateral Triangle Angle Measures) Each angle of an equilateral triangle measures 60 degrees
Created by: martha.kelley