4.1 Apply Congruence and Triangles 4.2 Prove Triangles Congruent by SSS, SAS Objectives: 1. To...

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4.1 Apply Congruence and Triangles 4.2 Prove Triangles Congruent by SSS, SAS Objectives: 1. To define congruent triangles 2. To write a congruent statement 3. To prove triangles congruent by SSS, SAS

Transcript of 4.1 Apply Congruence and Triangles 4.2 Prove Triangles Congruent by SSS, SAS Objectives: 1. To...

Page 1: 4.1 Apply Congruence and Triangles 4.2 Prove Triangles Congruent by SSS, SAS Objectives: 1. To define congruent triangles 2. To write a congruent statement.

4.1 Apply Congruence and Triangles4.2 Prove Triangles Congruent by SSS, SAS

Objectives:1. To define congruent triangles2. To write a congruent statement3. To prove triangles congruent by SSS,

SAS

Page 2: 4.1 Apply Congruence and Triangles 4.2 Prove Triangles Congruent by SSS, SAS Objectives: 1. To define congruent triangles 2. To write a congruent statement.

Congruent Polygons

Page 3: 4.1 Apply Congruence and Triangles 4.2 Prove Triangles Congruent by SSS, SAS Objectives: 1. To define congruent triangles 2. To write a congruent statement.

Congruent Triangles (CPCTC)

Two triangles are congruent congruent triangles triangles if and only if the ccorresponding pparts of those ccongruent ttriangles are ccongruent.

• Corresponding sides are congruent

• Corresponding angles are congruent

Page 4: 4.1 Apply Congruence and Triangles 4.2 Prove Triangles Congruent by SSS, SAS Objectives: 1. To define congruent triangles 2. To write a congruent statement.

Congruence Statement

When naming two congruent triangles, order is very important.

Page 5: 4.1 Apply Congruence and Triangles 4.2 Prove Triangles Congruent by SSS, SAS Objectives: 1. To define congruent triangles 2. To write a congruent statement.

Example

Write a congruence statement for the congruent triangles below.

Page 6: 4.1 Apply Congruence and Triangles 4.2 Prove Triangles Congruent by SSS, SAS Objectives: 1. To define congruent triangles 2. To write a congruent statement.

Example

Which polygon is congruent to ABCDE?ABCDE -?-

Page 7: 4.1 Apply Congruence and Triangles 4.2 Prove Triangles Congruent by SSS, SAS Objectives: 1. To define congruent triangles 2. To write a congruent statement.

Properties of Congruent Triangles

Page 8: 4.1 Apply Congruence and Triangles 4.2 Prove Triangles Congruent by SSS, SAS Objectives: 1. To define congruent triangles 2. To write a congruent statement.

Example

What is the relationship between C and F?

30

30

75

75

E

F

D

A

C

B

Page 9: 4.1 Apply Congruence and Triangles 4.2 Prove Triangles Congruent by SSS, SAS Objectives: 1. To define congruent triangles 2. To write a congruent statement.

Third Angle Theorem

If two angles of one triangle are congruent to two angles of another triangle, then the third angles are also congruent.

Page 10: 4.1 Apply Congruence and Triangles 4.2 Prove Triangles Congruent by SSS, SAS Objectives: 1. To define congruent triangles 2. To write a congruent statement.

Congruent Triangles

Checking to see if 3 pairs of corresponding sides are congruent and then to see if 3 pairs of corresponding angles are congruent makes a total of SIX pairs of things, which is a lot! Surely there’s a shorter way!

Page 11: 4.1 Apply Congruence and Triangles 4.2 Prove Triangles Congruent by SSS, SAS Objectives: 1. To define congruent triangles 2. To write a congruent statement.

Congruence Shortcuts?

Will one pair of congruent sides be sufficient? One pair of angles?

Page 12: 4.1 Apply Congruence and Triangles 4.2 Prove Triangles Congruent by SSS, SAS Objectives: 1. To define congruent triangles 2. To write a congruent statement.

Congruence Shortcuts?

Will two congruent parts be sufficient?

Page 13: 4.1 Apply Congruence and Triangles 4.2 Prove Triangles Congruent by SSS, SAS Objectives: 1. To define congruent triangles 2. To write a congruent statement.

Congruent Shortcuts?

Will three congruent parts be sufficient?

And if so….what three parts?

Page 14: 4.1 Apply Congruence and Triangles 4.2 Prove Triangles Congruent by SSS, SAS Objectives: 1. To define congruent triangles 2. To write a congruent statement.

Investigation…

… Using 2,3,4 Triangles

Page 15: 4.1 Apply Congruence and Triangles 4.2 Prove Triangles Congruent by SSS, SAS Objectives: 1. To define congruent triangles 2. To write a congruent statement.

Side-Side-Side Congruence Postulate

SSS Congruence Postulate:SSS Congruence Postulate:If the three sides of one triangle are

congruent to the three sides of another triangle, then the two triangles are congruent.

Page 16: 4.1 Apply Congruence and Triangles 4.2 Prove Triangles Congruent by SSS, SAS Objectives: 1. To define congruent triangles 2. To write a congruent statement.

SSS Congruence Postulate

Page 17: 4.1 Apply Congruence and Triangles 4.2 Prove Triangles Congruent by SSS, SAS Objectives: 1. To define congruent triangles 2. To write a congruent statement.

A B

C

D

Using a 2-Column Proof!

Is ABC is congruent to ABD? Why or why not?

Page 18: 4.1 Apply Congruence and Triangles 4.2 Prove Triangles Congruent by SSS, SAS Objectives: 1. To define congruent triangles 2. To write a congruent statement.

Example

Decide whether the triangles are congruent. Explain your reasoning.

Page 19: 4.1 Apply Congruence and Triangles 4.2 Prove Triangles Congruent by SSS, SAS Objectives: 1. To define congruent triangles 2. To write a congruent statement.

Investigation…

Part 2

Page 20: 4.1 Apply Congruence and Triangles 4.2 Prove Triangles Congruent by SSS, SAS Objectives: 1. To define congruent triangles 2. To write a congruent statement.

Congruence Shortcuts

Side-Angle-Side (SAS) Congruence Side-Angle-Side (SAS) Congruence Postulate:Postulate:

If two sides and the included angle of one triangle are congruent to two sides and the included angle of another triangle, then the two triangles are congruent.

Page 21: 4.1 Apply Congruence and Triangles 4.2 Prove Triangles Congruent by SSS, SAS Objectives: 1. To define congruent triangles 2. To write a congruent statement.

Can we prove?...yet?

Page 22: 4.1 Apply Congruence and Triangles 4.2 Prove Triangles Congruent by SSS, SAS Objectives: 1. To define congruent triangles 2. To write a congruent statement.

What else would we need?

Page 23: 4.1 Apply Congruence and Triangles 4.2 Prove Triangles Congruent by SSS, SAS Objectives: 1. To define congruent triangles 2. To write a congruent statement.

Can we Prove Triangle Congruence?

Page 24: 4.1 Apply Congruence and Triangles 4.2 Prove Triangles Congruent by SSS, SAS Objectives: 1. To define congruent triangles 2. To write a congruent statement.

Another Proof…?

Page 25: 4.1 Apply Congruence and Triangles 4.2 Prove Triangles Congruent by SSS, SAS Objectives: 1. To define congruent triangles 2. To write a congruent statement.

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