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Fig. 841.15A
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Fig. 841.15B
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841.15
We now take any point, J, on the spherical surface
circle scribed by the
divider's point B around its rotated point at P. We
now know that K is equidistant
chordally from P and from the center of the sphere.
With point A of our dividers on J, we
strike point K on the same surface circle as J, which
makes J equidistant from K, P, and X,
the center of the sphere. Now we know by construction
integrity that the spherical radii
XJ, XK, and XP are the same length as one another and
as the spherical chords PK, JK,
and JP. These six equilength lines interlink the four
points X, P, J, and K to form the
regular equiedged tetrahedron. We now take our straightedge
and run it chordally from
point J to another point on the same surface circle
on which JK and K are situated, but
diametrically opposite K. This diametric positioning
is attained by having the chord-
describing straightedge run inwardly of the sphere and
pass through the axis PP',
emerging from the sphere at the surface-greatcircle
point R. With point A of the dividers
on point R of the surface circle__on which also lies
diametrically point K__we swing point
B of the dividers to strike point S also on the same
spherical surface circle around P, on
which now lie also the points J, K and R, with points
diametrically opposite J, as is known
by construction derived information. Points R, S, P,
and X now describe another regular
tetrahedron equiedged with tetrahedron JKPX; there is
one common edge, PX, of both
tetrahedra. PX is the radius of the spherical, octahedrally
constructed sphere on whose
surface the circle was struck around one of its three
perpendicularly intersectioned axes,
and the three planes through them intersect congruently
with the three axes by
construction. PX is perpendicular to the equatorial
plane passing through W, Y, W', Y' of
the spherical octahedron's three axes PP', WW', and
YY'.
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