tic <- function(x) {sec <-proc.time()[3]  # passano x sec
       while(proc.time()[3] < sec+x) sec <- sec}
dev.new(width=6, height=3)
f <- function(x) sin(x)
ang <- 0; dang <- pi/24
while (ang < 3.2*pi) {
par(mfrow=c(1,2), mar=c(3,2,2,1))
# parte sinistra
plot(c(-1,1),c(-1,1),type="n",xlab="", ylab="", asp=1)
abline(v=axTicks(1), h=axTicks(2), col="blue",lty=3)
symbols(0,0, circles=1, inches=FALSE, add=TRUE, fg="red")
ang <- ang+dang; points(c(0,cos(ang)), c(0,sin(ang)) )
lines(c(0,cos(ang)), c(0,sin(ang)), lty=3 )
lines(c(1,0), c(0,0), col="red")
lines(c(cos(ang),cos(ang)), c(0,sin(ang)) ,lwd=2)
text(cos(ang)*.7,sin(ang)*.7,"x",col="red")
text(cos(ang),sin(ang)/2,"I",col="white")
text(cos(ang),sin(ang)/2,"sin",col="red",font=4)
# parte destra
plot(c(0,10),c(-1,1),type="n",xlab="", ylab="")
abline(v=axTicks(1), h=axTicks(2), col="blue",lty=3)
abline(v=0, h=0, col="blue",lty=2)
abline(v=seq(pi/2,3*pi,pi/2),lty=2, col="red")
plot(f,0,ang,add=TRUE,lwd=2); points( ang,sin(ang) )
tic(1/3)}