Question

In ∆ABC shown below, AB is congruent to BC.

Given: AB = BC. Prove:

Prove: The base angles of an isosceles triangle are congruent.

The two-column proof with missing statement proves the base angles of an isosceles triangle are congruent.

Answer 1

I found the additional attachment of this problem.

The question was Which statement can be used to fill in the numbered blank space.

The number blank space is number 3 under the Statement column. The Reason column stated that number 3 is Reflexive property.
                                        __     __
The missing statement is BD ≡ BD

The above triangle can be divided into two equal triangle when we cut it along the line BD. Thus, the reflexive property of congruence.