Note on opposite angles formed by two crossing lines
Two lines crossed in an X, captioned 'opposite angles'; headed 'fifteen'
Little was entered on this verso: two straight lines cross in the form of an X and are captioned 'opposite angles', with the word 'fifteen' set above as a proposition number. The crossing illustrates the equality of vertically opposite angles. The rest of the leaf shows only faint show-through from adjacent pages.
On this page
Vertically opposite angles at a crossing
Two lines cross in an X and the figure is labelled 'opposite angles', the pair of angles that face each other across the intersection. The heading 'fifteen' numbers it as a proposition in the running sequence.