In the study of junior high school mathematics, circles and semicircles are very common figures. I have sorted out their perimeter formula and area formula. Come and have a look with me.

The formula of circumference length and area C=2πr

S=(πr 2 )÷2

Semi-circle perimeter and area formula C=πr+2r

S=(πr 2 )÷2

The formula of spherical surface area and volume S=4πr 2

V=(4/3)πr ^3

The above is the formula about circle and ball that I compiled for you. I hope it can help you.