The sphere: Surface area and volume

The figure resulting from rotating a circle fixed by a diameter is called a sphere like the one we can see in the following picture:

The volume of a sphere has the following expression: $$V=\dfrac{4}{3}\pi \cdot r^3$$

To remember the expression of the area of the sphere, it is useful to remember that it is the derivative of the volume according to $r$ $$A=4 \cdot \pi \cdot r^2$$