# Copia tutto e incolla in R
tic <- function(x) {sec <-proc.time()[3]; while(proc.time()[3] < sec+x) sec<-sec} # passano x sec
plot(c(0,10),c(0,10),type="n",xlab="",ylab="")
text(5,6,"E' un'ELLISSE o una PARABOLA ?"); text(5,4,"Osserva l'animazione e rispondi")
tic(5); n<- 200; i<-0; for (k in 0:n) {
 tic(0.1);x <- c(0,10); y <- c(0,10);
 {z <- array(c(0,0,0,0),dim=c(2,2))};
 {pr<- persp(x,y,z,xlim=c(0,10),ylim=c(0,10),zlim=c(0,10),phi=0+i,theta=-30)};
 x <- c(0,10); for(k in seq(1,9,1)) lines(trans3d(x,z=0,y=k,pmat=pr),col="grey");
 y <- c(0,10); for(k in seq(1,9,1)) lines(trans3d(x=k,z=0,y,pmat=pr),col="grey");
 {x<-seq(-20,30,len=200);lines(trans3d(x,z=0,y=(x-5)^2,pmat=pr),col="red");i<-i+40/n}}
 tic(2); i<-0; for (k in 0:n) {tic(0.03);x <- c(0,10); y <- c(0,10);
 {z <- array(c(0,0,0,0),dim=c(2,2))};
 {pr<- persp(x,y,z,xlim=c(0,10),ylim=c(0,10),zlim=c(0,10),phi=40-i,theta=-30)};
 x <- c(0,10); for(k in seq(1,9,1)) lines(trans3d(x,z=0,y=k,pmat=pr),col="grey");
 y <- c(0,10); for(k in seq(1,9,1)) lines(trans3d(x=k,z=0,y,pmat=pr),col="grey");
 {x<-seq(-20,30,len=200);lines(trans3d(x,z=0,y=(x-5)^2,pmat=pr),col="red");i<-i+40/n}
}
# Fine