The width of this rectangle is approximately half the circumference of the circle, which is πr. Its height is approximately r. So its area is approximately πr x r = πr 2. That’s just an approximation, ...

So the circumference of the circle is 2 r Pi Here is what we do: So now we take the slices and rearrange them into a rectangular like thing. The height is "r" because it is the same length as the ...

The curved surface is like the label around a tin of soup – it can be flattened out to make a rectangle. The length of the rectangle is the same as the circumference of the circular ends (\(2\pi ...

The length of the rectangular face is the circumference of the circular face. Remember that the circumference of a circle \(= \pi \times d\) and the diameter \(= 2 \times \text{radius}\).