🧠 Can a centuries-old theorem unlock the secret to this modern geometry puzzle? 🎯 In this video, we explore a powerful but often forgotten theorem from 1643, credited to the great philosopher and mathematician René Descartes. This elegant geometric formula allows us to calculate the radius of a circle nestled between three others — a mind-blowing application of pure mathematics! ✍️ We’ll walk through the puzzle, reveal how Descartes’ Circular Theorem works, and show you how surprisingly effective it still is nearly 400 years later. 🔴 Can you find the radius of the red circle before the solution is revealed? Whether you're a math lover, a puzzle fan, or just here for a brain teaser with a historical twist — this is a challenge you don’t want to miss! 📌 Chapters: 0:00 Intro 1:01 Kissing Circle Theorem Explained 6:21 What is I don't know this theorem? 👇 Drop your answer in the comments before watching the full solution! ✨ Don't forget to like, comment, and subscribe for more awesome math puzzles and clever problem-solving adventures! Join the Chanel 👉 -------------------------------------------------------------- 📧 Contact Me: ✉️ thephantomofthemath@ -------------------------------------------------------------- Music by Helkimer - original - #MathPuzzle #GeometryChallenge #DescartesTheorem #ShadedArea #MathHistory #HiddenGemsInMath #ForgottenTheorem