Question

ssume ∠ACB and ∠ECD are not congruent. The Vertical Angles Theorem says that vertical angles must be congruent. Since this contradicts the assumption, vertical angles ACB and ECD are congruent.
Is the indirect proof logically valid? If so, why? If not, why not?

Yes. Statements are presented in a logical order using the correct theorems.

Yes. The conclusion was used to contradict the assumption.

No. The conclusion was used to contradict the assumption.

No. The progression of the statements is logically inaccurate.