How do you prove area of a circle?
Integrate an incremental area
dArea = r dr dTheta from r=0 to R, and Theta from zero to 2PI radians.
Area= INT INT dTheta rdr dTheta
Area= 2PI (1/2 R^2)= PI R^2
Integrate an incremental area
dArea = r dr dTheta from r=0 to R, and Theta from zero to 2PI radians.
Area= INT INT dTheta rdr dTheta
Area= 2PI (1/2 R^2)= PI R^2