Geometry comes to the rescue here.

this is not geometry, this is practical life experience. i dont think geometry expert can do this.

This is how to use Mathematics in real life

第二个场景为啥不用前面的那个圆盘划线？

But I dont think I will refind this video in that particular future case when I need it 😞

I prefer to credit the art of measurement

Real angles.

Smart!

the first part of the video: Weird place to even put a bump