Known square diagonal two points for another two points

Squares, known (X0,Y0) and (X2,y2) can be obtained according to the following relationship (X1,y1), (x3,y3) x1+x3 = x0+x2;x1-x3 = Y2-y0;y1+y3 = Y0+y2;y1-y3 = x0-x2; node[0].p[1].x = ((node[0].p[0].x+node[0].p[2].x) + (NODE[0].P[2].Y-NODE[0].P[0].Y))/2; node[0].p[1].y = ((NODE[0].P[0].Y+NODE[0].P[2].Y) + (node[0].p[0].x-node[0].p[2].x))/2; node[0].p[3].x = ((node[0].p[0].x+node[0].p[2].x)-(NODE[0].P[2].Y-NODE[0].P[0].Y))/2; node[0].p[3].y = ((NODE[0].P[0].Y+NODE[0].P[2].Y)-(node[0].p[0].x-node[0].p[2].x))/2;

The same with the known rectangle three points to ask for another point

node[0].p[3].x = node[0].p[2].x + (node[0].p[0].x-node[0].p[1].x);
NODE[0].P[3].Y = Node[0].p[2].y + (NODE[0].P[0].Y-NODE[0].P[1].Y);

See POJ3449 for details.

Known square diagonal two points for another two points