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How draw a circle in Lua?

How can draw a circle by drawing point?

local x, y = 0, 0
for i = 1, 360 do
    drawPoint( (x*i), (y*i) )
end

I'm bad at math.

local x, y = 0, 0
for i = 1, 360 do
    drawPoint( math.cos(i)*(10)+x, math.sin(i)*(10)+y )
end

Ok I did it; But I have some questions:

  1. How do I know the appropriate number place number 40 in the a loop?

  2. How do I know width, and radius? Which represents the number 10 in the loop.

Let's say x and y is your centre co-ordinate and r is the radius. Now:

local x, y, r = 0, 0, 1
for i = 1, 360 do
  local angle = i * math.pi / 180
  local ptx, pty = x + r * math.cos( angle ), y + r * math.sin( angle )
  drawPoint( ptx, pty )
end

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