In ∆ABC shown below, line segment AB is congruent to line segment BC.. . Given: line segment AB≅line segment BC. . 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.. . . Which statement can be used to fill in the numbered blank space?. . Answers. ∡DBA ≅ ∡CDB. . ∡CAB ≅ ∡ACB. . ∡ABD ≅ ∡DBC. . ∡BDA ≅ ∡BDC