In this diagram, cd is the perpendicular bisector of ab. the two-column proof shows that ac is congruent to bc. which of the following would justify step 6?
step 1 : cd is the perpendicular bisector of ab. justification: given
step 2: ad =`` bd (ad is congruent to bd). justification: definition of bisector
step 3: cd is congruent to cd. justification: reflexive property of congruence
step 4: adc and bdc are right angles. justification: definition of perpendicular lines
step 5: adc is congruent to bdc. justification: all right angles are congruent.
step 6: adc is congruent to bdc. justification: ?
step 7: ac is congruent to bc. justification: cpctc
which of the following would justify step 6?
a) aas
b) asa
c) sas
d) sss