1. Congruence and Triangles

2. Congruent Figures
• Two plane figures are congruent if they
are the same size and shape - that is, if
their corresponding angles are equal and
their corresponding sides are equal.
http://www.math.com/school/subject3/lessons/S3U3L1GL.html

3. ∠A P≅ ∠
∠B Q≅ ∠
∠C R≅ ∠
Corresponding Angles
Corresponding Sides
PQAB ≅
QRBC ≅
PRAC ≅

4. Example 1
Corresponding Angles
Corresponding Sides
a. Find the value of x.
b. Find the value of y.
∠D K≅ ∠
∠E L≅ ∠
∠F M≅ ∠
∠G N≅ ∠
KLDE ≅
LMEF ≅
MNFG ≅
KNDG ≅

5. Theorem 4.3 – Third Angles Theorem
• If two angles of one
triangle are congruent
to two angles of
another triangle, then
the third angles are
congruent.

6. Example 2- Using the 3rd
Angle Theorem
• Find the value of x in the diagram.

7. Example 3 – Determining whether triangles are congruent
• Decide if the triangles are congruent.
Justify your reasoning.

8. Homework
• Exercise 4.2 page 205: 1-39,
odd.