A treatise on special or elementary geometry (1877)
Olney, Edward, 1827-1887, Olney, Edward, 1827-1887. Elements of trigonometry, plane and spherical · New York : Sheldon · leaf 283
Fig. 402. 264 EXERCISES IN GEOMETRICAL INVENTION. … Fig. 403. Tlie Regular Icosaedron.—Taking20 equal equilateral triangles, theycan be grouped in two sets, as intlie figure, in a manner alt6getbersimilar to the preceding case. Thesolid angles in this case are includedby 5 facial angles whose sum is 3^right angles (?), which is a possiblecase (Part…
Geometry · Trigonometry
Internet Archive · California Digital Library · Public Domain Mark 1.0. Free to use for anything.
