gistfile1.txt

/**
  * Arrow 'plugin' for Raphael
  **/
  MySystem.arrow_path = function(startx,starty,endx,endy,len,angle) {    
    var theta = Math.atan2((endy-starty),(endx-startx));
    var baseAngleA = theta + angle * Math.PI/180;
    var baseAngleB = theta - angle * Math.PI/180;
    var tipX = endx + len * Math.cos(theta);
    var tipY = endy + len * Math.sin(theta);
    var baseAX = endx - len * Math.cos(baseAngleA);
    var baseAY = endy - len * Math.sin(baseAngleA);
    var baseBX = endx - len * Math.cos(baseAngleB);
    var baseBY = endy - len * Math.sin(baseAngleB);
    var pathData = " M " + tipX      + " " + tipY +
                   " L " + baseAX  + " " + baseAY +
                   " L " + baseBX  + " " + baseBY +
                   " Z ";
    return pathData;
  };