feat(geometry/euclidean/basic): lemmas about angles and distances (#7140)
feat(geometry/euclidean/basic): lemmas about angles and distances (#7140)





Co-authored-by: Johan Commelin <759412786bc533369b22377bf83fb9056c5b25b2@commelin.net>

leanprover-community/mathlib,leanprover-community/mathlib