original.R

# Instruction to students: You may clear the code in this file and replace it
# with your own.

library(tidyverse)
library(ggforce)
theme_set(theme_void())

# Draw a random chord in a unit circle centred at origin -----------------------

# Coordinates of equilateral triangle
eqtri_df <- tibble(
  x    = c(0, sqrt(3) / 2, -sqrt(3) / 2),
  y    = c(1, -0.5, -0.5),
  xend = c(sqrt(3) / 2, -sqrt(3) / 2, 0),
  yend = c(-0.5, -0.5, 1)
)

# Coordinates of random chord
rdmchr_df <- tibble(
  x    = 0.93636368,
  y    = 0.35103142,
  xend = -0.9999991,
  yend = -0.001326758
)

# Plot
p <- ggplot() +
  ggforce::geom_circle(aes(x0 = 0, y0 = 0, r = 1), col = "gray50") +
  geom_segment(data = eqtri_df, aes(x = x, y = y, xend = xend, yend = yend)) +
  geom_segment(data = rdmchr_df, aes(x = x, y = y, xend = xend, yend = yend),
               col = "red3") +
  coord_equal()

ggsave(p, file = "plot.png", height = 5, width = 7)