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Section 4-2
Some Ways to
Prove Triangles
Congruent
POSTLATES:
1. SSS Postulate
(Side-Side-Side)
If three sides of one
triangle are congruent to
three sides of another
triangle, then the triangles
are congruent.
Example:
C
D
F
A
B
E
By SSS Postulate,
ABC  DEF
2. SAS Postulate
(Side-Angle-Side)
If two sides and the included
angle of one triangle are
congruent to two sides and
the included angle of
another triangle, then the
triangles are congruent.
Example:
B
A
D
C
By SAS Postulate,
ABD  CDB
3.ASA Postulate
(Angle-Side-Angle)
If two angles and the
included side of one
triangle are congruent to
two angles and the
included side of another
triangle, then the triangles
are congruent.
Example:
D
B
C
E
A
By ASA Postulate,
ABC  DEC