Book ten. Propositions 85-90. A couple things, first of all,

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Book ten.

Propositions 85-90.

A couple things, first of all, why is the porism on proposition six constantly referenced? In the case of the former pair, it is always BC and CD, square numbers, and the latter is just another whole and annex squared. This would make more sense if there were a triplet of proportional lines for the former case because then the square lines could be as the first to the last.

But barring that, my second concern is in the vein of how they are used. Like why isn't
the whole squared : annex squared :: whole number : larger square number

Instead it's 'smaller square number : whole number', which doesn't make any logical sense.