a) Xét \(\Delta ABD\) và \(\Delta CAE\) có:
\(\left\{{}\begin{matrix}AB=AC\left(gt\right)\\\widehat{ABD}=\widehat{CAE}\end{matrix}\right.\Rightarrow\Delta ABD=\Delta CAE\left(ch-gn\right)\)
b) \(\Delta ABD=\Delta CAE\left(cmt\right)\)
\(\Rightarrow BD=AE;CE=AD\)
\(\Rightarrow BD+CE=AE+AD=BD\)