Finding the center of a circle allows you to solve basic geometry problems; for example, to find the circumference or area of the circle itself. There are several ways to identify this point! You can draw crisscross lines, draw overlapping circles, or use a ruler or ruler.
Steps
Method 1 of 3: Drawing Cross Lines
Step 1. Draw a circle
Use a compass and draw the edge of any circular object. Size matters. If you need to find the center of a given circle, you don't need to perform this step.
A geometric compass is a specific tool designed to draw and measure circles. Buy one at a stationery or office supply store
Step 2. Draw a chord between two points
A chord is a straight segment that joins two points belonging to a curved line. Name the string as the AB segment.
Use a pencil to draw the lines. This way you can delete them once you find the center. Draw them lightly so it will be easier to get rid of them
Step 3. Draw a second string
This must be parallel and of equal length to the previous one. Name this other string as the CD segment.
Step 4. Draw another line connecting point A with point C
This third string (AC) should pass through the center of the circle, but to locate it precisely you need a fourth line.
Step 5. Join point B with D
Draw the final chord (BD) joining points B and D. This should intersect the AC chord drawn earlier.
Step 6. Find the center
If you have drawn straight segments precisely, then the center of the circle is at the intersection point between the AC and BD strings. Mark the center point using a pen or pencil. If you only need the center, you can erase the strings you drew earlier.
Method 2 of 3: Using Overlapping Circles
Step 1. Draw a chord between two points
Use a ruler or ruler to draw a line inside the circle that joins two points on the circumference. The choice of points does not matter, but identify them with the letters A and B.
Step 2. With a compass draw two overlapping circles
These must be exactly identical. The first has point A as its center and the second point B. Spacer them so that they overlap as in a Venn diagram.
Draw these circles with a pencil and not a pen. The process will be easier if you can delete the secondary circles later
Step 3. Draw a vertical line joining the two intersection points of the circles
There should be a point above and below the "Venn diagram" space created by the overlapping circles. To do this, use a ruler and make sure the straight line passes both points of intersection. Finally, name the two points (C and D) where the new straight line meets the original circumference. This line also identifies the diameter of the starting circle.
Step 4. Erase the two overlapping circles
By doing this, the drawing will be simpler and clearer to proceed with the next steps. At this point you should have a circle with two perpendicular lines crossing it. Do not delete the centers (A and B) of the overlapping circles; they will be needed to draw two new circles.
Step 5. Draw two new circles
Use the compass to draw two new identical circles: the first will have point C as its center and the second point D. These will overlap forming a sort of Venn diagram. Remember that C and D are the points where the vertical line meets the main circle.
Step 6. Draw a line through the points where the new circles meet
It is a straight, horizontal line that cuts through the overlapping space of the circles. This also corresponds to the second diameter of the original circumference which is perfectly perpendicular to the first.
Step 7. Find the center
The point of intersection between the two diameters is the center of the circle! Use a reference mark. If you want to clean up the design, delete the secondary circles and diameters.
Method 3 of 3: Using a Row and a Team
Step 1. Draw two straight lines tangent to the circumference and intersecting
These can be completely random, but to make the process easier they should be as perpendicular to each other as possible.
Step 2. Drag both lines to the other side of the circle
At the end you should have one circle and four tangents that form a rough parallelogram or rectangle.
Step 3. Draw the diagonals of the parallelogram
The intersection point of the diagonals represents the center of the circle.
Step 4. Check the accuracy of the bearing with the help of a compass
If you make no mistake when transferring the two initial tangents, you shouldn't have any difficulty finding the perfect center of the circle. At the end you can delete the diagonals and the parallelogram.
Advice
- Try using graph paper instead of white or lined paper. This way you can use perpendicular lines and squares as references.
- You can also find the center of a circle with a mathematical process of "completing the square". This method is useful if you have been made aware of the circumference equation, but are not working with a real physical circle.
Warnings
- To find the "true" center of a circle you need a compass and a ruler.
- Ruler and ruler are not the same thing: the ruler is any instrument with a straight edge and a uniform surface. The ruler reports also a graduated scale. You can turn a ruler into a handy ruler by drawing reference marks every centimeter.
