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Objective: The students will be able to identify congruent triangles, find corresponding parts of congruent triangles and transform congruent triangles.

Chapter 4 – Lesson 2 Congruent Triangles

Vocabulary Corresponding Matching according to some agreed rule

Definition Congruent Triangles We say triangles ABC and DEF are congruent if and only if all their corresponding parts are congruent (CPCTC) We write ABC  DEF A corresponds to D; B to E; C to F

ARCHITECTURE A tower roof is composed of congruent triangles all converging toward a point at the top. Name the corresponding congruent angles and sides of HIJ and LIK. HIJ LIK Answer: Since corresponding parts of congruent triangles are congruent, Example 3-1a

Name the congruent triangles. ARCHITECTURE A tower roof is composed of congruent triangles all converging toward a point at the top. Name the congruent triangles. Answer: HIJ LIK Example 3-1b

The support beams on the fence form congruent triangles. b. Name the congruent triangles. a. Name the corresponding congruent angles and sides of ABC and DEF. Answer: Answer: ABC DEF Example 3-1c

Vocabulary Congruence Transformation A function that changes a triangle into a new triangle congruent to the original We’ll look at 3 congruence transformations: Slide Turn Flip

Congruence Transformation Slide Slides are often called translations

Congruence Transformation Turn Turns are often called rotations

Congruence Transformation Flip Flips are often called reflections

Answer: RST is a turn of RST. COORDINATE GEOMETRY The vertices of RST are R(─3, 0), S(0, 5), and T(1, 1). The vertices of RST  are R(3, 0), S(0, ─5), and T(─1, ─1). Name the congruence transformation for RST and RST. Answer: RST is a turn of RST. Example 3-2d

b. Name the congruence transformation for ABC and ABC. Answer: turn Example 3-2g

Theorem 4.3 Third Angle Theorem If two angles of a triangle are congruent to two angles of a second triangle then the third angles of the two triangles are also congruent

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Lesson Summary: Objective: The students will be able to identify congruent triangles, find corresponding parts of congruent triangles and transform congruent triangles.

Preview of the Next Lesson: Objective: The students will be able to Prove Congruence – SSS and SAS.

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