Question

why radius of curvature is always positive

Answer 1

Explanation:

The distance from the vertex to the center of curvature is the radius of curvature of the surface. If the vertex lies to the left of the center of curvature, the radius of curvature is positive. If the vertex lies to the right of the center of curvature, the radius of curvature is negative.

Answer 2

Answer:

The distance from the vertex to the center of curvature is the radius of curvature of the surface. If the vertex lies to the left of the center of curvature, the radius of curvature is positive. If the vertex lies to the right of the center of curvature, the radius of curvature is negative.