FOCAL_POINT <- 5
NUM_CURVES <- 10

x <- seq(-0.2, 10, by = 0.1)
y <- (1/(4*FOCAL_POINT))*x^2
plot(x, y, type = "l", xlim=c(-1, 10), asp = 1, col = 1)
#plot(x, y, type = "l", xlim=c(-12 - 4*FOCAL_POINT, 12 + 4*FOCAL_POINT), asp = 1, col = 1)
points(0, FOCAL_POINT, pch = 1)
grid()

for (i in 1:NUM_CURVES){
    x <- seq(-10 - 4*i, 10 + 4*i, by = 0.2)
    d <- (4*FOCAL_POINT) + 4*i
    y <- (1/d) * (x^2) - i
    lines(x, y, col = i + 1)
    print(paste0("Focal Point:  ", ((d/4)-i)))
}