My proof done on my whiteboard and digitally cleaned. Reference: The proved statement is a case of the geometric mean theorem: https://en.wikipedia.org/wiki/Geometric_mean_theorem Thales' theorem: https://en.wikipedia.org/wiki/Thales%27s_theorem Inscribed Similar Triangles: https://k12.libretexts.org/Bookshelves/Mathematics/Geometry/07%3A_Similarity/7.11%3A_Inscribed_Similar_Triangles
