4.6 Using Congruent Triangles

Corresponding parts of congruent triangles are congruent.

*Special case of definition of congruent figures.

*Used after proving triangles congruent.

CPCTC

Statements Reasons

1. <1 ≡ <22. <ABC suppl. <1 <DEC suppl <23. < ABC ≡ < DEC4. <ACB ≡ <DCE5. 6. ACB ≡ DCE7. .

1. Given2. Angles in a linear pair are ≡.3. Suppl. Of ≡ <s are ≡.4. Vertical <s are ≡ .5. Given6. AAS ≡7. CPCTC

The triangles are congruent by ASA. CPCTC says that AB= DE. If you can measure length of DE, then you will know the length of AB.

The supplements of < 1 and <2 are congruent. DE is reflexive.

∆ DEB ≡ ∆ DEC by AAS.

DB ≡ DC because of CPCTC.

AD is reflexive. This makes ∆ ABD ≡ ∆ ACD by SAS.

Geometry

• Page 257(1-14, 28, 41-43)

• Page 259 (18-24, 29-31, 33-35, 44-46)