Technical Drawing with Engineering Graphics, 15th Edition

3 Useful Formulas for Geometric Entities

Formulas for Circles

The formulas associated with a circle, a sector of a circle, segment of a circle, and a circular ring are shown, with a pictorial representation for each. The first figure shows a circle with its radius indicated as lowercase r, and the diameter indicated as lowercase d. A small arc is indicated along the circumference of the circle. The associated formulas are given, and they are: area (represented as uppercase A) equals pi times r squared; A equals 3.141 times r squared; A equals 0.7845 times d squared; diameter (represented as lowercase d) equals 2 times r; circumference (represented ...