A torus is a doughnut-shaped surface formed by revolving a circle around an axis outside the circle. It is a 3D shape with a hole in the center, characterized by two radii:
\[ A = \frac{\pi r^2 \alpha}{360} = \frac{br}{2} \]
This formula calculates the surface area of the torus. It represents the outer surface formed by the revolving circle.
\[ b = \frac{2 \pi r \alpha}{360} \]
This formula calculates the length of the base circle of the torus, which is essential for understanding the geometry and how the torus is formed.