source: CGBLisp/examples/midpoints.macsyma@ 1

if get('geometry,'version)=false then load(geometry);
x1:0;
y1:0;
y2:0;

/* Triangle */
A:[x1,y1];
B:[x2,y2];
C:[x3,y3];
M:[x,y];
P:[u1,v1];
Q:[u2,v2];
R:[u3,v3];
eqns:append([
        collinear(M,A,P),
        collinear(M,B,Q),
        collinear(M,C,R)
        ],
        append(
                midpoint(P,B,C),
                midpoint(Q,A,C),
                midpoint(R,A,B)
        )
);