quartz(height=4, width=3) # to the screen
plot(cos, -pi,  3*pi)

quartz(height=4, width=3) # to the screen
eq = function(x) { x**2}
curve(eq, xlim=c(0,25))
 x=(1:50)
y=eq(x)
plot(x, y,  xlab = "X-axis", ylab = "Y-axis")
curve(eq,xlim=c(0,10), add=T, col=2)