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