To conclude the proof, you should have a statement that encapsulates the main result or implication of your derivation. In this case, since you have shown that triangles ABD and CBD are similar (or congruent), you need to summarize this outcome effectively. A suitable statement could be:
"Thus, triangles ABD and CBD are similar (or congruent), which implies that the segments AB and BC are proportional, confirming that triangle ABC has the properties defined by its isosceles nature."
Alternatively, if your proof is intended to demonstrate the congruence of these triangles, you could conclude with:
"Therefore, triangles ABD and CBD are congruent by the SAS Congruence Theorem."
Make sure the final statement reflects the goal of your proof regarding the relationships within the triangles or any specific properties you aim to demonstrate.