https://www.geogebra.org/m/bZ5wQ3JQ
Circle & Circumference
version 2
NCTM illuminations - Slope Pi and Lines
https://illuminations.nctm.org/uploadedFiles/Content/Lessons/Resources/9-12/PiLine-AS-Slope.pdf
version 1
Is there another way to 'roll' the circle on a straight line? How?
圓弧問題 1
圓弧問題 2
https://www.geogebra.org/m/Rzx3X2Jb
GeoGebra Institute of Hong Kong - 圓周(學生版)
https://www.geogebra.org/m/wb5R89Wd