[NotYourLawyer]

It's not totally rigorous, but it wouldn't be hard to fill in the details. This is a sketch of a proof, not the proof itself.

[karthickgururaj]

Yes, that's basically what I said and meant in the parent post. I was suggesting the article call it a "graphical" solution approach, not analytical.

And if I wasn't clear - it wasn't my intent to treat this any less "useful". If anything, it is more interesting (for me) to read about solutions that give an intuitive feel, than dry analysis.

[n4r9]

Proofs can be graphical or diagrammatic, though. Take for example this proof of the Pythagorean Theorem: https://cdn.britannica.com/43/70143-004-CCB17706/theorem-dem...

[hgsgm]

"analytical" means "calculus" here.