CK-12 Geometry - Second Edition

4.5. Isosceles and Equilateral Triangles http://www.ck12.org

Fill in the blanks in the proofs below.

24.Given: Isosceles 4 CIS, with base angles^6 Cand^6 SIOis the angle bisector of^6 CISProve:IOis the perpen-

dicular bisector ofCS

TABLE4.19:

Statement Reason

1. Given


2. Base Angles Theorem
   3.^6 CIO∼=^6 SIO


3. Reflexive PoC


4. 4 CIO∼= 4 SIO
   6.CO∼=OS


5. CPCTC
   8.^6 IOCand^6 IOSare supplementary


6. Congruent Supplements Theorem
   10.IOis the perpendicular bisector ofCS

Write a 2-column proof.

25.Given: Equilateral 4 RSTwithRT∼=ST∼=RSProve: 4 RSTis equiangular