( 1034 j 
Of a trigonal prism are given the planes |’, (0110) and 1’, (1010), 
further J”, (OOOL). If one admits the latter plane as projection-plane, 
~ 
then becomes a, = a, ——; y = 120°. 
ej) 
_ 
A Y 
yy 
Wy 
Uf Yi 
ES 
Fig. 3. 
If further one measures between the traces of P‚:V, and V,:V, 
successively the angles /, = 76°, h, = — 53°, then furnishes (1) 
cot 76° == sin 5 td 0 
and 
cot 53° —= — sin 6 tg (uy — 120°) 
from which: 
8 cot 76° + cot 53° cot 76° 
tg vg — td Oo — = 
ty 60° cot 53° “Scot 53° 
t¢9 = 1,07592 of — 0,80754. 
From this the values are found: 
ga 47°5'58"; v‚— 1329542"; p= +. 162°54'17"; gj — 17°5'43" 
51893349"; G,—= 13°3340"; G,—= — 54°9'53"; og, = 549953" 
Be in fig. 3 AB the trace of V, (0001), then 
CDUY DOB=h,= 78") and UEI'(7 BOE = h, daj 
indicate the direction of the traces of WV, and WV, The plane 4, (g, 7, 
has its pole with regard to J’, in octant 1, coth, >0, 4, consequently 
lies in quadrant 1; with regard to V,, s, lies in octant IV, coth, <0, 
h, in quadrant 2, whilst 4,—=0, and the trace of J’, consequently 
shuts off the section at the top. Consequently the section @ corre- 
sponds to the secant-plane S,; in the same way one finds, that the 
