feat(geometry/euclidean/angle/sphere): affine circle theorems (#17279)
feat(geometry/euclidean/angle/sphere): affine circle theorems (#17279)

Add (oriented) Euclidean affine space versions of "angle at center of a circle equals twice angle at circumference" and "angles in same segment are equal" / "opposite angles of a cyclic quadrilateral add to π" (which were previously only present for angles between vectors, not for angles between points in an oriented Euclidean affine space).





leanprover-community/mathlib,leanprover-community/mathlib