From a regular octagon, a triangle is formed by connecting three randomly chosen vertices of the octagon. What is the probability that at least one of the sides of the triangle is also a side of the octagon?[asy]
size(3cm);
pair A[];
for (int i=0; i<9; ++i) {
A = rotate(22.5+45*i)*(1,0);
}
filldraw(A[0]--A[1]--A[2]--A[3]--A[4]--A[5]--A[6]--A[7]--cycle,gray,black);
for (int i=0; i<8; ++i) { dot(A); }
[/asy]<spanclass=′latex−bold′>(A)</span>72<spanclass=′latex−bold′>(B)</span>425<spanclass=′latex−bold′>(C)</span>1411<spanclass=′latex−bold′>(D)</span>75<spanclass=′latex−bold′>(E)</span>76 probability2018 AMC 8AMC 8