Consider the following proof of the Base Angles Theorem. Which statement should fill in the blank? PROOF: Given isosceles △ABC with AB¯¯¯¯¯¯¯¯≅BC¯¯¯¯¯¯¯¯, I can construct BD←→, the angle bisector of ∠B. _____________________. I also know that line segments are congruent to themselves, so BD¯¯¯¯¯¯¯¯≅BD¯¯¯¯¯¯¯¯ by the reflexive property of congruence. I now have two pairs of sides and an included angle that are congruent, so I know that △ABD≅△CBD by the SAS Congruence Theorem. Finally, corresponding parts of congruent triangles are congruent by the CPCTC Theorem, so ∠A≅∠C.(1 point)ResponsesThen, by the definition of an angle bisector, I know that ∠BAC≅∠BCA.Then, by the definition of an angle bisector, I know that angle upper B upper A upper C congruent to angle upper B upper C upper A .Then, by the definition of an angle bisector, I know that ∠ABD≅∠CBD.Then, by the definition of an angle bisector, I know that angle upper A upper B upper D congruent to angle upper C upper B upper D . Then, by the definition of a midpoint, I know that AD¯¯¯¯¯¯¯¯≅DC¯¯¯¯¯¯¯¯. Then, by the definition of a midpoint, I know that Modifying above upper A upper D with bar congruent to Modifying above upper D upper C with bar .Then, by the definition of an isosceles triangle, I know that AB¯¯¯¯¯¯¯¯≅CA¯¯¯¯¯¯¯¯.

Answer 1

The statement that should fill in the blank is:

"Then, by the definition of an angle bisector, I know that ∠ABD≅∠CBD."

This statement is appropriate because, by the construction of line segment BD as the angle bisector of ∠B, it guarantees that the two angles created, ∠ABD and ∠CBD, are equal. This equality is necessary for proceeding with the proof using the SAS Congruence Theorem to establish that the triangles ABD and CBD are congruent.