1. Lesson 4-2: Triangle Congruence – SSS, SAS, ASA, & AAS
Vocab
SSS (side-side-side) congruence
Included angle
SAS (side-angle-side) congruence

2. Draw the following figures using a ruler
Draw a triangle, measure its lengths
Draw another triangle in a different “manner” using the same length sides.
Are the 2 triangles different? Are they the same shape, same size?
They’re
Congruent!

3. SSS congruence If 3 sides are congruent to other 3 sides
→ ∆’s congruent by SSS (side-side-side)
Rule

4. Draw the following figures using a ruler
A triangle with a 900 angle. Measure only the 2 sides that touch the 900
Draw another triangle in a different “manner” using the 2 measured lengths and 900 angle between them
Are the 2 triangles different? Are they the same shape, same size?
They’re
Congruent!

5. SAS congruence
If 2 sides and the included angle between them are congruent to other 2 sides and the included angle
→ ∆’s congruent by SAS (side-angle
side) Rule
→ Look for SAS – list S or A in order 8 8
750
750 12 12

6. Examples In ∆VGB, which sides include B?
2. In ∆STN, which angle is included between
and ?
3. Which triangles can you prove congruent? Tell whether you would use the SSS or SAS Postulate. Y A P X B

7. 4. What other information do you need to prove ∆DWO ∆DWG?
5. Can you prove ∆ SED ∆BUT from the information given? Explain. D O G W U T D E S B

8. Proving Congruence in ∆’s
Go in a circle around triangle naming markings or measures in order (S or A)
∆’s congruent if :
SSS : all 3 sides
SAS : an angle between (included) 2 sides
ASA : a side between 2 angles
AAS : a side after 2 angles
NEW ONES!

9. What are the letter combinations we can’t use?
AAA
A$$

10. Hints Use facts/rules to find any missing angle or side measures first
Is a side congruent to itself?
Can you use any angle facts to find missing angle measures?
Look for parallel lines

11. Which side is included between R and F in ∆FTR?
2. Which angles in ∆ STU include ?
Tell whether you can prove the triangles congruent by ASA or
AAS. If you can, state a triangle congruence and the postulate
or theorem you used. If not, write not possible. 3. 4. 5. Q H G P I R P L
Quiz
Tomorrow!
4-1, 4-2
4-3 Y A A B C X