Mathematics for Carpenters and Builders - Carpenter's and Builder's Math, Plans, and Specifications - page 169

In Figure 5-53A,

3 2

√ 25

AB = + 4 2 = = 5 feet

In Figure 5-53B,

5 2 25

√ 16

BC = − 3 2 = − 9 = = 4 feet

B B

? ?

3 FT 3 FT

A C A C

(B)
Figure 5-53 To find the length of any side of a right triangle
given the other two sides.

(A)

Problem 2
To find the length of the circumference of a circle.
Rule: Multiply the diameter by 3.1416.
Example What length of molding strip is required for a circular win-
dow that is 5 feet in diameter?
5

7 feet
Since the carpenter does not ordinarily measure feet in tenths, .7
should be reduced to inches. It corresponds to 8 1

× 3 . 1416 = 15 .

/ 2 inches from
Table 5-23. That is, the length of molding required is 15 feet
8 1

/ 2 inches.
Problem 3
To find the length of the arc of a circle.
Rule: Arc

central angle.
Example If the radius of a circle is 2 feet, what is the length of a
60 ◦ arc?

= .017453 × radius ×