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Drawing a path circle with actionscript and trigonometria

Hi:

I want animate a dot following a circle path using action script.

(Yeah... its easy to draw a circle path and create a motion tween... but i want to animate it using action script)

Im using this formula:

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var r = 150;

// r is the radius value

mover = function()

{

if( this._x >= -1*r && this._x <= r-1 && this._y >= 0 && this._y <= r)

// x will increase by 2 if the dot is located

// at x=-150 and x<149

// y = 0 and y <= 150

{

this._x +=2;

// increase x by 2 px

this._y = Math.sqrt ((r*r) - (this._x * this._x));

// I determine the y position using the trigonometria circle formula

}

else

{

this._x -=2;

this._y = (Math.sqrt ((r*r) - (this._x * this._x))) * (-1);

// I determine the y position using the trigonometria circle formula

// x will decrease by 2 if the dot is not located

// at x=-150 and x<149

// y = 0 and y <= 150

}

}

c1._x = -1*r;

// The dot is posted at coord x=-150

c1._y = 0;

// The dot is posted at Y=0

c1.onEnterFrame = mover;

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The formula works well... more or less...

check it and see how the dot follow the circle path, put it jumps just in the middle of the circle.