An algorithm problem about mathematical triangles, circles to find the coordinates of intersection points

Three existing and input conditions:
1. The radius of the known circle is r
2. The coordinates of the center of the circle (x1, y1) are known; 3. The
(x2, y2) of another point is known;

The coordinates of the intersection of the circles,

I forgot the triangle formula, the formula of the right triangle, please give the formula, now make a blue ball trend chart of two-color balls, you need to use this.