Given: Δ ABC ≅ Δ DEF

The corresponding line segments and the corresponding angles are congruent.

Methods to prove 2 triangles congruent:

• SSS• SAS• ASA• AAS

The following NEVER prove congruence:

• SSA• AAA

Geometry 4-3 Triangle Congruence

SSSI

D

E

I

D

E

I

D

E

• All 3 sides are ≅therefore the s are ≅

SASI

D

E

I

D

E

N

G

L

E

• 2 sides and their INCLUDED angle are ≅ therefore the s are ≅

* The angle MUST be between the 2 sides

ASAI

D

E

N

G

L

E

N

G

L

E

• 2 angles and their INCLUDED side are ≅ therefore the s are

≅

* The side MUST be between the 2 angles

AASI

D

E

N

G

L

E

N

G

L

E

• 2 angles and their NON-INCLUDED side are ≅ therefore the s are ≅

* The side CANNOT be between the 2 angles

1. 2.

Congruent or NOT Justification Congruent or NOT Justification

3. 4.

Congruent or NOT Justification Congruent or NOT Justification

H L • Must be a right triangle

• The hypotenuse and leg must be congruent to

the hypotenuse and leg of another right triangle

YPOTENUSE

EG

7. 8.