21/03/02 21:02:45.39 EygxTbXG.net
pizza_cut <- function(phi, r){
circle <- function(x) sqrt(r^2-x^2)
f <- function(x) integrate(circle,-r,x)$value
x=uniroot(function(x) f(x)- (pi*r^2/2)*(phi/(1+phi)),c(-r,r))$root
Plot(-r,r,bty='n')
Cir(0i,r)
seg(x-1i*circle(x),x+1i*circle(x),lty=5)
c(x=x,length=2*circle(x))
}
pizza_cut(2,30/2) # 直径30cｍのピザを2:1に分割
pizza_cut(1/2+sqrt(5)/2,1) # 半径1cmの金貨を黄金比に切断