f1 <- function(x) asin(x)
f2 <- function(x) acos(x)
f3 <- function(x) atan(x)
plot(f1,-1,1,ylim=c(-2,pi),col="blue",lwd=2,asp=1,n=1e4)
plot(f2,-1,1,asp=1,add=TRUE,lwd=2,n=1e4)
plot(f3,-6,6,asp=1,add=TRUE,lwd=2,col="red",n=1e4)
plot(f2,-1,1,asp=1,add=TRUE)
plot(f1,-1,1,col="blue",add=TRUE,asp=1)
abline(h=0,v=0)
abline(h=seq(-5,5,1),v=seq(-5,5,1),lty=3)
abline(h=pi,lty=2)
abline(h=-pi/2,lty=2)
abline(h=pi/2,lty=2)