function p = dscut(p1,y1,p2,y2)%function p = dscut(p1,y1,p2,y2)%return the point p at which y=0, assuming y varies linearly %from y1 at p1 to y2 at p2.k1 = y2./(y2-y1); k2 = 1-k1;n = size(p1,1);p = k1(ones(n,1),:).*p1 + k2(ones(n,1),:).*p2;