Mathematics for Carpenters and Builders - Carpenter's and Builder's Math, Plans, and Specifications - page 155

In Figure 5-30, draw any chord MS .
With M and S as centers, and with
any radius, describe arcs LF and L F ,
and draw a line through their inter-
section, giving a diameter AB . Apply-
ing the same construction with centers
A and B , describe arcs ef and e f .A
line drawn through the intersections of
these arcs will cut line AB at O , the
center of the circle.

C

A

B

D

Problem 10
To describe an arc of a circle with a
given radius through two given points.
In Figure 5-31, take the given points
A and B as centers, and, with the given radius, describe arcs that
intersect at C . From C , with the same radius, describe an arc AB ,
as required.

Figure 5-29 To bisect

an angle.

e
f

S

L' F'

L

F

0 B

A

e'

f'

M

Figure 5-30 Find the center of a circle.

Second Method
In Figure 5-32, for a circle or an arc, select three points ABC in
the circumference that are well apart. With the same given radius,
describe arcs from these three points that intersect each other, and
draw two lines, DE and FG , through their intersections. The point
where these lines intersect is the center of the circle or arc.
Problem 11
To describe a circle passing through three given points.