1. Warm Up
1. Name all sides and angles of ∆FGH.
2. What is true about K and L? Why?
3. What does it mean for two segments to be congruent?

2. The Idea of a Congruence
Two geometric figures with exactly the same size and shape. A C B D E F
Each triangle is made up of six parts:
3 sides and 3 angles

3. Corresponding Parts
If all six pairs of corresponding parts (sides and angles) are congruent, then the triangles are congruent. B A C
AB  DE
BC  EF
AC  DF
 A   D
 B   E
 C   F
ABC   DEF E D F

5. CPCTC Corresponding Parts of Congruent Triangles are Congruent.

6. Congruence Transformations
Congruency amongst triangles does not change when you…
slide (translation),
Turn (rotation),
or flip (reflection)
… the triangles.

7. EXAMPLE 1
Identify congruent parts
Write a congruence statement for the triangles. Identify all pairs of congruent corresponding parts.

8. Complete each congruence statement.

10. Write a congruence statement.

11. Given ΔBCD = ΔRST, m C = 57, m R = 64, m D = 5x + 4. Find x and m T.
Given ΔQRS = ΔLMN, RS = 8, QR=14, QS=10, MN = 3x – 25. Find x.

12. Name the corresponding angles and sides if ΔBCD = ΔEFG.
Given ΔCAT = ΔDOG, CA=14, AT=18, TC=21 and
DG=2x+7, find the value of x.

13. Given: ∆ABC  ∆DBC.
Find the value of x and
mDBC.

14. Given: ∆ABC  ∆DEF
Find the value of x.
Find mF.

15. 1. ∆ABC  ∆JKL and AB = 2x + 12. JK = 4x – 50. Find x and AB.
Lesson Quiz
1. ∆ABC  ∆JKL and AB = 2x JK = 4x – 50. Find x and AB.
Given that polygon MNOP  polygon QRST, identify the congruent corresponding part.
2. NO  ____ T  ____