To find the midpoint, or center, of a circle, follow these instructions:
Find two points on the circle that are completely opposite from each other, i.e., that is, they are separated by the diameter of the circle.
If you know their coordinates, add the two x coordinates together, and divide the result by 2. This is the x coordinate of the center.
Do the same for the 2 y coordinates, which will give you the y coordinate.
Combine the two to get the centroid’s coordinates.
If you do not know the coordinates, measure the distance between the two points and half it.
This half distance between one endpoint and the other is the midpoint.
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