Degrés et radians expliqués visuellement | Trigonométrie

In this video, we explain the radian in a clear and visual way using the unit circle. A radian is defined as the angle that subtends an arc whose length is exactly equal to the radius R of the circle. By laying the radius along the circumference, we can see what “1 radian” really means. Then we answer the key question: ✅ How many radians are there in a semicircle? In other words, how many radians correspond to 180°? By counting along the semicircle, we get: 1 radian 2 radians 3 radians plus a small remaining part (about 0.141592…) This leads to the famous result: 180° = 3.14… radians = π radians (an irrational number). Finally, we summarize the main degree–radian conversions: 90° = π/2 180° = π 360° = 2π 🎯 Perfect for high school students, beginners in trigonometry, and anyone who wants to understand radians instead of memorizing formulas.