In this video https://www.youtube.com/watch?v=WUvTyaaNkzM&list=PLZHQObOWTQDMsr9K-rj53DwVRMYO3t5Yr, at 2:45, why is the unraveled ring a trapezoid when it should clearly be a rectangle? I was thinking that in real life, the unraveled ring actually is a rectangle, but Grant is saying it's a trapezoid so that he can prove a point. The point he's proving is that if you increase the number of rings by a finite amount, the unraveled rings will look less like trapezoids and more like rectangles. And when you set the number of rings to approach infinity, the unraveled rings are rectangles, and so to find the area of the circle, you just add up an infinite amount of rectangles, which is also the area under the function $2\pi r$, which is $\pi r^2$. So, in real life, are the unraveled rings actually rectangles or not?
Also at 3:00, what does Grant mean when he says the circumference formula $2\pi r$ is the definition of pi?