hi, How to write a function that checks if the circle passes through four given points. plz give me the logic or concept for making this function.

Calculate the center of the circle (probably you have it :p). And calculate the distance of this points to the center. Mathematics

If you have radius and center cordinates then you can use the standred equation of circle. ((X- H)*(X -H)) + ((Y -K)*(Y - K)) = R*R H -> center x cordinate K -> center y cordinate R -> Radius X -> x cordinate of given point Y -> y cordinate of given point Make a function which take two arguments ( given point x and y cordinate) and return a bool flag ( true if circle passes through given point otherwise false). In function calculate X -H and get its sqrt (Given point X - Center Point X) calculate Y -K and get its sqrt add both result and compare with radius square if both equal the and get its sqrt Note : 1 : Please take care of floating point issues 2 : This is for one point you can extend for more points 3 : make a struct for point , that would be a good candidate like Code: struct point { int x, int y };