1. Warmup: One of the sides of an isosceles triangle is 6 cm. If another side is 12 cm, what is the greatest possible perimeter the triangle could have?

2. “HYPOTENUSE LEG” 4.6: CPCTC

3. With SSS, SAS, ASA, AAS, and HL, you know how to use three parts of triangles to show they are congruent. Once you have triangles congruent, you can make other conclusions about other parts, because, be definition, corresponding parts of congruent triangles are congruent. You can abbreviate this as CPCTC. Recall

4. Examples If ∆ARW~ΔQAZ, we know 6 things: In a proof, if you are asked to prove m<A=m<Q, if the triangles are congruent that contain them, you can write as your last step that m<A=m<Q because “they are corresponding parts of congruent triangles, so they must be congruent” or you can simply write “CPCTC.”

5. Ex. 1

7. *note*: To use CPCTC, you must have _________________. C P C T C