PROOF: Given isosceles △ABC

with AB¯¯¯¯¯¯¯¯≅BC¯¯¯¯¯¯¯¯
, I can construct BD←→
, the angle bisector of ∠B
. Then, by the definition of an angle bisector, I know that ∠ABD≅∠CBD
. 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.

What statement should be placed at the end of the proof?

(1 point)
Responses

 Finally, corresponding parts of congruent triangles are congruent by the CPCTC Theorem, so ∠A≅∠B
.
 Finally, corresponding parts of congruent triangles are congruent by the CPCTC Theorem, so angle upper A congruent to angle upper B .

Finally, corresponding parts of congruent triangles are congruent by the CPCTC Theorem, so AB¯¯¯¯¯¯¯¯≅BC¯¯¯¯¯¯¯¯
.
Finally, corresponding parts of congruent triangles are congruent by the CPCTC Theorem, so Modifying above upper A upper B with bar congruent to Modifying above upper B upper C with bar .

Finally, corresponding parts of congruent triangles are congruent by the CPCTC Theorem, so ∠A≅∠C
.
Finally, corresponding parts of congruent triangles are congruent by the CPCTC Theorem, so angle upper A congruent to angle upper C .

Finally, ∠A≅∠C
by the Base Angles Theorem.
Finally, angle upper A congruent to angle upper C by the Base Angles Theorem.

1 answer

The appropriate statement to place at the end of the proof is:

Finally, ∠A≅∠C by the Base Angles Theorem.
or
Finally, angle upper A congruent to angle upper C by the Base Angles Theorem.

This conclusion follows from the fact that in an isosceles triangle, the angles opposite the equal sides are congruent. Hence, since we have established that triangles ABD and CBD are congruent, it implies that the angles at A and C are also congruent.