Area of parts of circles

[lungulst]

Good video, short and clear. I will modify something though: I think it will be very helpful to write 0.25 and 0.75. Because if you want to calculate you will use 0.25 and 0.75 even if you are doing it yourself or on a calculator. (Yes on a calculator you can tap .25 but on the screen will appear 0.25). And there is another reason also: Maths should look the same in any language.