find an edge point of ellipse

Hi there,

I'm a software developer who started in business software and has been working in flash games for a while. I have recently started learning more about dynamic animation and the drawing api in action script. Unfortunately i'm still pretty new to a lot of the math concepts involved in things like inverse kinematics, and even more simply, the problem of this post which is how to draw ears on a cats head.

explanation: I'm creating a model of a cat for a game, using inverse kinematics, with a seperate class (or inheritedclass for some) each segment. i.e. Head/Torso/Upper leg/ forleg etc. so then i can pin these together and give them properties etc. and create a dynamically animated cat.

Working on the head I want to draw ears (triangular shape) onto a simple oval head shape.

so I have an oval. I know its width, height and the x,y of its center point (relative to the stage)

http://www.exceliyb.com/pic1.PNG

the image will be rotated to be at an angle which i know the degrees of:

http://www.exceliyb.com/pic2.PNG

what i want to be able to do is check wether a given x,y co-ordinate intersects the circumference of the circle. or figure out all points (x,y) that make up the circumference. pretty much i want the base of the ears to touch perfectly without overlap the cat "skull" (oval). So in the picture below i would have needed to know that point A and B were both on the circumference of the circle to be able to draw the ear there with code:

http://www.exceliyb.com/pic3.PNG

does anyone know a formula/s that could help me with this. Thanks very much for any help anyone can give in advance. This is my first post on this site so if I've inadvertantly made a complete fool of myself with a stupid question i apologise for that in advance as well :)

~ Jazz