Sometimes in a drawing or painting you need to find the center of a circle. This technique is mathematically correct, but as an artist I just eyeball the distances.
Keep on practicing and you will manage it real quick.
- Get your circle
- Draw at least three lines intersecting the circle.
- Find the halfway point of those lines.
- Draw a 90 degree line from that halfway-point.
- The middle of the circle is where those lines intersect.