var AC = sqrt((ax-x)^2 + (ay-y)^2)
var BC = sqrt((bx-x)^2 + (by-y)^2)
var AB = sqrt((ax-bx)^2 + (ay-by)^2)
var CH = abs((ay-by)*x - (ax - bx)*y + ax*by - bx*ay)/AB
var cosCAB = ((ax-x)*(ax - bx) + (ay - y)*(ay - by))/(AC*BC)
var cosCBA = ((bx-x)*(bx - ax) + (by - y)*(by - ay))/(AB*BC)
if (cosCAB < 0) { return AC}
else if (cosCBA < 0) {return BC}
else {return CH}