
On Bilinear Functions 15
applied on the local coordinates y, corresponds an identical orthogonal substitution
Y8 = 2CqbsqEq
applied to the tangential coordinates Y. Given this, suppose that between the x's and y's
one institutes the n- 1 relations that result from setting equal the n ratios
Y" (, = I, 2,
...'0.
ClrXl +
C2rX2 + ... +
CnrXn
This is equivalent to considering two homographic stars with centers on the points 0 and
0 ~. With such hypotheses, the equation
ylY1 + y2Y2 + ... + ynY,~ = 0,
which corresponds to this other equation in the ~?-axis system
~?IE1 + rl2E: ...