Finding normal vector on circles

[_Seven_]

Hi everyone.

Having a circle, knowing its center and radius, how can I calculate the normal vector? I need more information? Moreover, how can I calculate a tangent vector to the circle, knowing its center, radius and the normal vector?

If I rotate this circle, it is possible to calculate again the normal vector with the same direction? Because the normal vector can be pointing in opposite directions.

Thank you very much for your help.

 

[arildno]

The normal vector at one point on the circle will be a different vector than the normal vector at some other point on the circle.

Only straight planes have the same normal vector at all its points.

 

[mathman]

The normal vector at any point on the circumference is along the radius vector to the point. It can be in either direction (outward or inward).