Answer:
use SSS
Explanation:
Given two congruent chords AB and BC in circle O, you want to prove ∆AOB is congruent to ∆COB.
Statement . . . . Reason
1. circle O, AB≅BC . . . . given
2. OB ≅ OB . . . . reflexive property of congruence
3. OA ≅ OC . . . . definition of a circle
4. ∆AOB ≅ ∆COB . . . . SSS postulate
__
Additional comment
Your erased statement 2 shows you know exactly how to do this.
All the radii of a circle are the same length, so it is easy to show congruence by SSS, given that AB≅BC.