This is a historical flowchart proof about the Nagel Point theorem.
It shows the logical chains of propositions and how the proof of:

• Nagel Point theorem depends on the theorems: Ceva, and Semiperimeter & Excircles.

• Ceva's theorem depends on the Menelaus theorem.

• Menelaus theorem depends on Similarity of triangles and a transversal, etc.

For more details: click on the buttons Nagel Point, Ceva's theorem, Menelaus theorem, or Semiperimeter & Excircles.