toroidal surface

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The normal of any point on a toroidal surface passes through the rotation axis of this surface. Now there are 3 points (close together) on the surface, which make a (small, planar) triangle. I am looking for a point on this triangle from where the normal of the triangle also passes through the axis of the toroidal surface. I tried with the center of the circumscribed circle of the triangle, but this is not the correct point. the question is: is there a general rule to find the footpoint for the normal on the triangle, without using the surface.enter image description here