Proof: By Euclid

(related to Proposition: 2.12: Law of Cosines (for Obtuse Angles))


Thank you to the contributors under CC BY-SA 4.0!

Github:
bookofproofs
non-Github:
@Fitzpatrick


References

Adapted from (subject to copyright, with kind permission)

  1. Fitzpatrick, Richard: Euclid's "Elements of Geometry"