Easy Method to Find the Center of a Circle

Circles have an unusual geometry: they are the most regular, most symmetrical shape possible; but because there are no corners, finding one's center is more harder than you might expect. To find the precise center of a square or rectangle, you only need to draw lines from the opposite corners: the center is the point where they cross. The trick to finding a circle's center is creating corners of your own and using them. For small circles, all you need is a piece of paper, book or  some other object with a right-angle corner. If the circle is larger, a sheet of plywood or some other solid rectangle will do the trick.

What You'll Need
• A piece of paper large enough to reach across your circle
• Pencil
• Straightedge




Instructions
1)  Lay the sheet of paper on the circle so that one corner just touches the circle's perimeter. Hold the paper firmly and use the pencil to mark the exact points where the two edges of the paper cross the circle's outline.

2)  Connect the marks a ruler or other straightedge and draw a pencil line between them. Your line passes through the center.
3)  Rotate the paper and lay it on the circle at a different angle.
4)  Make the two new tick marks and connect them with another pencil line.






The circle's center is where the two lines cross.

Warning:
The corner you use must be a right angle or this exercise will not work.