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Mathematics

730Classifying Triangles by Sides
731Classifying Triangles by Angles
732Triangle Angle Sum Theorem
733Exterior Angle Theorem
734Base Angles of Isosceles Triangles
735Converse of Isosceles Triangle Theorem
736Properties of Equilateral Triangles
737Triangle Inequality Theorem
738Medians, Altitudes, and Angle Bisectors
739Centroid, Orthocenter, Incenter, and Circumcenter
740Congruent Triangles: Definition and Notation
741SSS (Side-Side-Side) Congruence Postulate
742SAS (Side-Angle-Side) Congruence Postulate
743ASA (Angle-Side-Angle) Congruence Postulate
744AAS (Angle-Angle-Side) Congruence Theorem
745HL (Hypotenuse-Leg) Congruence Theorem
746Why AAA and SSA Don't Work
747CPCTC: Corresponding Parts of Congruent Triangles
748Writing Two-Column Congruence Proofs
749Proving Overlapping Triangles Congruent
750Congruence in Isosceles and Equilateral Triangles
751Applications: Constructing Congruent Figures
752Definition of Similar Triangles
753AA Similarity Criterion
754SAS Similarity Criterion
755SSS Similarity Criterion
756Scale Factor in Similar Triangles
757Finding Missing Sides Using Similarity
758Similar Triangles in Nested Figures
759Parallel Lines and Triangle Similarity
760Perimeter and Area Ratios of Similar Triangles
761Applications and Proofs with Similar Triangles
762Introduction to Geometric Proof
763Two-Column Proof Format
764Paragraph Proof Format
765Flow Chart Proof Format
766Common Reasons in Proofs
767Proof by Contradiction
768Direct Proof Techniques
769Auxiliary Lines and Constructions
770Proving Theorems About Lines and Angles
771Proving Properties of Parallel Lines
772Multi-Step Proof Strategies

Mathematics

730Classifying Triangles by Sides
731Classifying Triangles by Angles
732Triangle Angle Sum Theorem
733Exterior Angle Theorem
734Base Angles of Isosceles Triangles
735Converse of Isosceles Triangle Theorem
736Properties of Equilateral Triangles
737Triangle Inequality Theorem
738Medians, Altitudes, and Angle Bisectors
739Centroid, Orthocenter, Incenter, and Circumcenter
740Congruent Triangles: Definition and Notation
741SSS (Side-Side-Side) Congruence Postulate
742SAS (Side-Angle-Side) Congruence Postulate
743ASA (Angle-Side-Angle) Congruence Postulate
744AAS (Angle-Angle-Side) Congruence Theorem
745HL (Hypotenuse-Leg) Congruence Theorem
746Why AAA and SSA Don't Work
747CPCTC: Corresponding Parts of Congruent Triangles
748Writing Two-Column Congruence Proofs
749Proving Overlapping Triangles Congruent
750Congruence in Isosceles and Equilateral Triangles
751Applications: Constructing Congruent Figures
752Definition of Similar Triangles
753AA Similarity Criterion
754SAS Similarity Criterion
755SSS Similarity Criterion
756Scale Factor in Similar Triangles
757Finding Missing Sides Using Similarity
758Similar Triangles in Nested Figures
759Parallel Lines and Triangle Similarity
760Perimeter and Area Ratios of Similar Triangles
761Applications and Proofs with Similar Triangles
762Introduction to Geometric Proof
763Two-Column Proof Format
764Paragraph Proof Format
765Flow Chart Proof Format
766Common Reasons in Proofs
767Proof by Contradiction
768Direct Proof Techniques
769Auxiliary Lines and Constructions
770Proving Theorems About Lines and Angles
771Proving Properties of Parallel Lines
772Multi-Step Proof Strategies

← Mathematics

Lesson 766 of 3,121·18. Geometry — Triangles and ProofPro lesson

Common Reasons in Proofs

Using definitions, postulates, theorems, and properties as valid reasons in geometric proofs.

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