You can put this solution on YOUR website! Since cd is perpendicular to AB we have two right triangles
cad and cbd
Since cd bisects ab then ad =db
we have
ad^2+cd^2=ca^2
and
db^2+cd^2=cb^2
but since
ad=db then
ad^2=db^2
therefore
ad^2+cd^2=db^2+cd^2
hence
ca^2=cb^2
therefore
ca=cb
QED