3.7 Angle Side Theorems. Theorem 20: Isosceles Triangle Theorem (ITT) If 2 sides of a triangle are congruent, then the angles opposite the sides are congruent.

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Presentation transcript:

3.7 Angle Side Theorems

Theorem 20: Isosceles Triangle Theorem (ITT) If 2 sides of a triangle are congruent, then the angles opposite the sides are congruent. A BC A BC Ifthen

Theorem 21: Converse Isosceles Triangle Theorem (CITT) If 2 angles of a triangle are congruent, then the sides opposite the angles are congruent. A BC A BC Ifthen

Can you prove theorems 20 &21? ITT can be proven using SSS by naming the triangle in a correspondence with itself. CITT can be proven using ASA by naming the triangle in a correspondence with itself. Special Note: for triangles, equilateral and equiangular will be used interchangeably.

Given: Prove: E F G H D Statements Reasons Given If then 3. SAS 4. CPCTC CITT

Given: Prove: X Z Y 1 2 Statements Reasons 1. Given If then 3.If 2 angles form a straight line, then they are supplementary 4.If 2 angles are supplementary to congruent angles then they are congruent ITT 4. ST

More Practice Proofs