Hatfield, Robert Griffith, 1815-1879. [from old catalog] · New York & London, Wiley and Putnam · leaf 35
Fig. 34. 77.—To bisect an angle. Let a b c, {Fig. 34,) be the angle to be bisected. Upon 6, with any radius, describe the arc, a c; upon a and c, with a radius greater than half a c, describe arcs cutting each other at d ; join b and d; and b d will bisect the angle, a 6 c, as was required. This… … Fig. 35. 78.—To trisect a right angle. Upon a, {Fig. 35,) with any radius, describe the arc, b c ; upon b and c, with the same radius, describe arcs cutting the arc, 6 c, at c? and e ; from d and e, draw lines to a, and they will trisect the angle as was required. The truth of this is made evident…
Carpentry · Architecture
Internet Archive · Library of Congress · Public Domain Mark 1.0. Free to use for anything.
![An illustration from L'optique divisée en trois livres : ou, l'On démontre d'une maniere aisée tout ce qui regarde 1. la propagation & les proprietez de la lumiere. 2. La vision. 3. La figure & la disposition des verres qui servent à la perfefectionner [sic] (1682)](https://img.insideoutlibrary.com/img/200/ia-loptiquedivise00ango-172-16.webp)
