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16 Cards in this Set
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Acute Triangle

All angles are acute. (Less than 90 degrees.)


Obtuse Triangle

One angle is obtuse. (Greater than 90 degrees.)


Right Triangle

One angle is right. (Equals 90 degrees.)


Scalene Triangle

No two sides of a triangle are congruent.


Isosceles Triangle

At least two sides of a triangle are congruent.


Equilateral Triangle

All sides of a triangle are congruent.


Angle Sum Theorem

The sum of the measures of the angles of a triangle is 180 degrees.


Third Angle Theorem

If two angles of one triangle are congruent to two angles of a second triangle, then the third angles of the triangles are congruent.


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.


Definition of Congruent Triangles
(CPCTC) 
Two triangles are congruent iff (if and only if) their corresponding parts are congruent.
(Corresponding Parts of Congruent Triangles are Congruent  CPCTC) 

Congruence of Triangles is:

Reflexive,
Symmetric and Transitive 

SSS Postulate
(SideSideSide) 
If the sides of one triangle are congruent to the sides of a second triangle, then the triangles are congruent.


ASA Postulate
(AngleSideAngle) 
If two angles and the included side of one triangle are congruent to two angles and an included side of another triangle, then the triangles are congruent.


AAS Postulate
(AngleAngleSide) 
If two angles and a nonincluded side of one triangle are congruent to the corresponding two angles and side of a second triangle, then the two triangles are congruent.


Isosceles Triangle Theorem

If two sides of a triangle are congruent, the the angles opposite those sides are congruent.


Converse of the Isosceles Triangle Theorem

If two angles of a triangle are congruent, then the sides opposite those angles are congruent.
