Equation for geting the position of dots in the circle of radius(r) & position(x, y)?

Question

I want to know how to draw a circle by using black color points in 'c' programing (by using for loop) for that i want to know its equation

Answer 1

I'll write the code in VB but it should look really similar in C.

The "PointOn(x, y)" function can be substituted by whatever you use.
Given radius r and center (x, y):

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For i = x -r to x +r

PointOn(i, y+(r^2 - x^2)^(1/2)))
PointOn(i, y -(r^2 - x^2)^(1/2)))

Next i
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Answer 2

(rcosa,rsina) represents the co-ordinates of any point on the circle.where r is the radius of the circle.and a is the angle made by the line joining the point and the centre with the horizon.
probably run the loop by varying a from 0 to 360 degrees and print the dot using gotoxy function as per dos compiler..
plz take care while doing the program

Answer 3

(x-a)^2+(y-b)^2

Answer 4

y=sqrt(r^2-x^2);
y=-sqrt(r^2-x^2)