Assertion: coordinate's value | /r/HasProperty | well-defined
Facets:
value: well
type: DEGREE
Source sentences:
text: For example, the origin in the polar coordinate system (r,θ) on the plane is singular, because although the radial coordinate has a well-defined value (r = 0) at the origin, θ can be any angle, and so is not a well-defined function at the origin.