This is incomplete, but it should be a start.
r=10; % triangle radius
p0=[0 0]; % prior point [x,y]
p=[50 50]; % current point [x,y]
% offset angle based on distance vector
% this may already be known from prior triangle orientation
th=atan2d(p(2)-p0(2),p(1)-p0(1))+180;
% calculate vertex locations
xv=r*cosd(th+[0 120 240 0]) + p(1);
yv=r*sind(th+[0 120 240 0]) + p(2);
% plot this triangle
plot(xv,yv)
xlim([0 100])
ylim([0 100])
axis equal
