Question 475809
{{{drawing(200,200,0,10,0,10,


line(1,1,5,7),
line(5,7,9,1),
locate(1,1,A),
locate(5,7,C),
locate(9,1,E),
locate(3,4,B),
locate(7,4,D)

)
}}}

We have AC = EC, and B is the midpoint of AC, D is the midpoint of EC. Hence we can say that BC = AC/2. Similarly, DC = EC/2. We now know that BC = DC because AC/2 = EC/2 (taken from our first equation).