The Sheet metal worker's instructor : for zinc, sheet iron, copper, and tin plate workers, and others, containing a selection of geometrical problems, also practical and simple rules for describing the various patterns required in the different branches of the above trades (1906)
Warn, Reuben Henry · Philadelphia : Henry Carey Baird & Co. · leaf 235
162 line B 2 will bisect the angle A b c — that is to say, the angle A b 2 will be equal to the angle 2bc. Fig. 42. To trisect (divide into three equal angles) a right angle A b c (Fig. 43) : With centre b, and any radius, describe the arc 1,2; with the centres 1 and 2, and the same radius,… … B C the arcs 3 and 4. Draw b 3 and b 4, and the right angle will be trisected or divided into three equal angles.
Sheet-metal work
Internet Archive · Getty Research Institute · Public domain (published before 1931). Free to use for anything.
