source("http://macosa.dima.unige.it/r.R")
f <- function(x) sin(x)
ang <- 0; dang <- pi/24
dev.new(width=6, height=3)
rowcol(1,2)
while (ang < 3.2*pi) {
 # left
 Boxm_(-1,1, -1,1)
 circl(0,0, 1, "red")
 ang <- ang+dang; POINT(c(0,cos(ang)), c(0,sin(ang)), "blue" )
 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)
 # right
 Box_(0,10, -1,1)
 abline(v=seq(pi/2,3*pi,pi/2),lty=3, col="red",lwd=2)
 plot(f,0,ang,add=TRUE,lwd=2); POINT( ang,sin(ang), "blue")
 wait(1/3)
}