3G EH0HB01IEDEAL SYSTEM. FIO. 47. 9TT 14 , X , ^ combi ? atio " s rhombohedrons with the forms m 211, the faces of a direct rhombohedron truncate the edses formed by 111 and each of the faces 217 T9T k / inverse rhombohedron truncate the ed f ’ , , ot an each of the faces 211, Th P ^ fTf by 111 and cate the solid angle in which the J ° rm 111 trun ' ill makes eoual anele? •«. ges V meet ' A normal to ■>» «» «™ faces llH. 2 JedST 1 *° of >” f°™ ill is called the ans of the rhombohedron. Mk(L ^X Combmatl °n of the forms 21I, n ° mal t0 an 7 ^ce of the nomal to th m mgle 90 ° ~ * with a •»a“"nde\°S'‘d“ ° f , thc f «-™ 2lI > tie fcro nit 7, ",° f cosr = sin30°sinT. z&Xis. 101 “ (% - “>■ *• o°f Ss f ? f e £ “ 2 ’ + 2 V. 14o. The rhombohedron 100 (fig. 49), is direct. 100,111 = D. 146. The rhombohedron 011 (fig. 5 o), is inverse. The f f tanx = — JtanD. form loo^ 8 ° the form 011 tr nncate the edges v of the FIG. 48. FIG. 49. FIG. 60. Oil. The faces of ThTfimm TTt 18 dlrGct - tanT = ftanD. K term 211 truncate the edges v of the forr The rhombohedron ,11 is direct, tanx = ftann.
