diff --git a/web/app/arc.js b/web/app/arc.js
index 3f983c3d..0c046d75 100644
--- a/web/app/arc.js
+++ b/web/app/arc.js
@@ -7,6 +7,7 @@ TCAD.TWO.Arc = function(a, b, c) {
   a.parent = this;
   b.parent = this;
   c.parent = this;
+  this.r = new TCAD.TWO.Ref();
 };
 
 TCAD.TWO.utils.extend(TCAD.TWO.Arc, TCAD.TWO.SketchObject);
@@ -36,9 +37,17 @@ TCAD.TWO.Arc.prototype.translateImpl = function(dx, dy) {
   this.c.translate(dx, dy);
 };
 
+TCAD.TWO.Arc.prototype.distanceA = function() {
+  return TCAD.math.distance(this.a.x, this.a.y, this.c.x, this.c.y);
+};
+
+TCAD.TWO.Arc.prototype.distanceB = function() {
+  return TCAD.math.distance(this.b.x, this.b.y, this.c.x, this.c.y);
+};
+
 TCAD.TWO.Arc.prototype.drawImpl = function(ctx, scale) {
   ctx.beginPath();
-  var r = TCAD.math.distance(this.a.x, this.a.y, this.c.x, this.c.y);
+  var r = this.distanceA();
   ctx.arc(this.c.x, this.c.y, r,
     Math.atan2(this.a.y - this.c.y, this.a.x - this.c.x),
     Math.atan2(this.b.y - this.c.y, this.b.x - this.c.x));
@@ -53,7 +62,7 @@ TCAD.TWO.Arc.prototype.visit = function(h) {
 };
 
 TCAD.TWO.Arc.prototype.normalDistance = function(aim) {
-  return 1000;
+  return -1000;
 };
 
 
@@ -106,6 +115,9 @@ TCAD.TWO.AddArcTool.prototype.mouseup = function(e) {
   } else if (this.point.id === this.arc.a.id) {
     this.point = this.arc.b;
   } else {
+    var arc = this.arc;
+    this.viewer.parametricManager.system.push(new TCAD.TWO.Constraints.P2PDistanceV(arc.b, arc.c, arc.r));
+    this.viewer.parametricManager.system.push(new TCAD.TWO.Constraints.P2PDistanceV(arc.a, arc.c, arc.r));
     this.viewer.toolManager.releaseControl();
   }
 };
diff --git a/web/app/canvas.js b/web/app/canvas.js
index 7e6673df..4219fb56 100644
--- a/web/app/canvas.js
+++ b/web/app/canvas.js
@@ -299,6 +299,18 @@ TCAD.TWO.SketchObject.prototype.draw = function(ctx, scale) {
   if (this.marked) ctx.restore();
 };
 
+TCAD.TWO.Ref = function() {
+  this.value = 0;
+};
+
+TCAD.TWO.Ref.prototype.set = function(value) {
+  this.value = value;
+};
+
+TCAD.TWO.Ref.prototype.get = function() {
+  return this.value;
+};
+
 TCAD.TWO.Param = function(obj, prop) {
   this.id = TCAD.TWO.utils.genID();
   this.obj = obj;
@@ -619,8 +631,16 @@ TCAD.TWO.DragTool.prototype.mousewheel = function(e) {
 
 TCAD.TWO.DragTool.prototype.solveRequest = function(fineLevel) {
   var locked;
-  if (this.obj._class == 'TCAD.TWO.EndPoint') {
+  if (this.obj._class === 'TCAD.TWO.EndPoint') {
     locked = [this.obj._x, this.obj._y];
+    if (this.obj.parent != null
+      && this.obj.parent._class === 'TCAD.TWO.Arc') {
+
+      if (this.obj.id != this.obj.parent.c.id) {
+        locked.push(this.obj.parent.c._x);
+        locked.push(this.obj.parent.c._y);
+      }
+    }
   } else {
     locked = [];
   }
diff --git a/web/app/constr/constraints.js b/web/app/constr/constraints.js
index f2542fc8..286b47e8 100644
--- a/web/app/constr/constraints.js
+++ b/web/app/constr/constraints.js
@@ -1,6 +1,6 @@
 TCAD.constraints = {};
 
-TCAD.constraints.create = function(name, params, constants) {
+TCAD.constraints.create = function(name, params, values) {
   switch (name) {
     case "equal":
       return new TCAD.constraints.Equal(params);
@@ -9,9 +9,11 @@ TCAD.constraints.create = function(name, params, constants) {
     case "parallel":
       return new TCAD.constraints.Parallel(params);
     case "P2LDistance":
-      return new TCAD.constraints.P2LDistance(params, constants[0]);
+      return new TCAD.constraints.P2LDistance(params, values[0]);
     case "P2PDistance":
-      return new TCAD.constraints.P2PDistance(params, constants[0]);
+      return new TCAD.constraints.P2PDistance(params, values[0]);
+    case "P2PDistanceV":
+      return new TCAD.constraints.P2PDistanceV(params);
   }
 }
 
@@ -137,14 +139,14 @@ TCAD.constraints.P2PDistance = function(params, distance) {
 
   this.get = function(i) {
     return this.params[i].get();
-  }
+  };
 
   this.error = function() {
     var dx = this.get(this.p1x) - this.get(this.p2x);
     var dy = this.get(this.p1y) - this.get(this.p2y);
     var d = Math.sqrt(dx * dx + dy * dy);
-    return (d - this.distance);
-  }
+    return (d - this.distance());
+  };
 
   this.gradient = function(out) {
 
@@ -159,6 +161,44 @@ TCAD.constraints.P2PDistance = function(params, distance) {
 
 };
 
+
+TCAD.constraints.P2PDistanceV = function(params) {
+
+  this.params = params;
+
+
+  this.p1x = 0;
+  this.p1y = 1;
+  this.p2x = 2;
+  this.p2y = 3;
+  this.d = 4;
+
+  this.get = function(i) {
+    return this.params[i].get();
+  };
+
+  this.error = function() {
+    var dx = this.get(this.p1x) - this.get(this.p2x);
+    var dy = this.get(this.p1y) - this.get(this.p2y);
+    var d = Math.sqrt(dx * dx + dy * dy);
+    return (d - this.get(this.d));
+  };
+
+  this.gradient = function(out) {
+
+    var dx = this.get(this.p1x) - this.get(this.p2x);
+    var dy = this.get(this.p1y) - this.get(this.p2y);
+    var d = Math.sqrt(dx * dx + dy * dy);
+    out[this.p1x] = dx / d;
+    out[this.p1y] = dy / d;
+    out[this.p2x] = -dx / d;
+    out[this.p2y] = -dy / d;
+    out[this.d] = -1;
+  }
+
+};
+
+
 TCAD.constraints.Parallel = function(params) {
 
   this.params = params;
diff --git a/web/app/parametric.js b/web/app/parametric.js
index 78578f90..f5a141c4 100644
--- a/web/app/parametric.js
+++ b/web/app/parametric.js
@@ -100,6 +100,12 @@ TCAD.TWO.ParametricManager.prototype.p2lDistance = function(objs, promptCallback
   }
 };
 
+TCAD.TWO.utils.constRef = function(value) {
+  return function() {
+    return value;    
+  };
+};
+
 TCAD.TWO.ParametricManager.prototype.p2pDistance = function(objs, promptCallback) {
   var p = this._fetchTwoPoints(objs);
   var distance = new TCAD.Vector(p[1].x - p[0].x, p[1].y - p[0].y).length();
@@ -108,7 +114,7 @@ TCAD.TWO.ParametricManager.prototype.p2pDistance = function(objs, promptCallback
   if (promptDistance != null) {
     promptDistance = Number(promptDistance);
     if (promptDistance == promptDistance) { // check for NaN
-      this.add(new TCAD.TWO.Constraints.P2PDistance(p[0], p[1], promptDistance));
+      this.add(new TCAD.TWO.Constraints.P2PDistance(p[0], p[1], TCAD.TWO.utils.constRef(promptDistance)));
     }
   }
 };
@@ -315,3 +321,17 @@ TCAD.TWO.Constraints.P2PDistance.prototype.getSolveData = function() {
   this.p2.collectParams(params);
   return ['P2PDistance', params, [this.d]];
 };
+
+TCAD.TWO.Constraints.P2PDistanceV = function(p1, p2, d) {
+  this.p1 = p1;
+  this.p2 = p2;
+  this.d = d;
+};
+
+TCAD.TWO.Constraints.P2PDistanceV.prototype.getSolveData = function() {
+  var params = [];
+  this.p1.collectParams(params);
+  this.p2.collectParams(params);
+  params.push(this.d);
+  return ['P2PDistanceV', params];
+};
\ No newline at end of file