How to draw a half circle on a plot?

I am trying to draw some half circles on a plot, using the trigonometric functions in R.
So here is what I have :

matPoints <<- as.data.frame(cbind(X=c(-1, -(sqrt(3)/2), -(sqrt(2)/2), -0.5, 0, 0.5, sqrt(2)/2, sqrt(3)/2, 1), Y=c(0, 0.5, sqrt(2)/2, sqrt(3)/2, 1, sqrt(3)/2, sqrt(2)/2, 0.5, 0)))

plot(x = matPoints$X*W, y = matPoints$Y*W)

For the moment, it prints each point on the plot. What I want to do here is to trace a smooth line between points so it gives me a beautiful half circle of center (0, 0) and of scale W.

Any solution?

>Solution :

Do you mean this?

x <- seq(0, pi, length.out = 500)
W <- 3
plot(cos(x) * W, sin(x) * W, type = "l")