in the chapter "Main laws of rational trigonometry", we reed:

Then the spread "s" between "L1" and "L2" is:
" s = s(L1,L2) = Q(B,C)/Q(A,C) = Q/R "
This ratio is clearly independent of the choice of "B" by Thales' theorem.

It'should be written: " s = s(L1,L2) = Q(B,C)/Q(A,B) = Q/R "

alexwajn
alexwajn