Download Geometry Section 5.3 Proving Triangles Congruent by SAS

Geometry Section 5.3
Proving Triangles Congruent by SAS
What you will learn:
1.Use the Side-Angle-Side Congruence
Theorem
2. Solve real-life problems
To show that two triangles are congruent
using the definition of congruent polygons, as
we did in the proof at the end of section 5.2,
we need to show that all ______
6 pairs of
corresponding parts are congruent. Theorem
5.5 allows us to prove triangles congruent
using only ______
6 pairs of corresponding
parts.
Before we look at Theorem 5.5, however, we
need to discuss what is meant by an included
angle.
is formed by the 2 sides
PE
I
two sides and the included angle
two sides and the
included angle
Notice there are two triangles with an angle of 25
and sides of lengths 19 and 8, but the triangles are
not congruent.
Example 2: Determine whether each pair of
triangles can be proven congruent by using
the congruence postulates. If so, write a
congruence statement and identify the
postulate used. None is a possible answer.
SAS
ATR  CKR
NOT SAS
No congruent
triangles
SAS
ETI  GHI
SAS
GRF  GRO
1) BC  DA, BC || AD
1)Given
2)BCA  CAD
2)Alt. Int. Angles Theorem
3) AC  AC
3)Reflexive Prop.
)ABC  CDA
) SAS
HW: pp 249 -250 / 6-17, 23, 26