Page:First six books of the elements of Euclid 1847 Byrne.djvu/74

QUAL triangles and on the same base () and on the same side of it, are between the same parallels.

If , which joins the vertices of the triangles, be not || , draw || meeting .

Draw .

Because || (const.)

= (pr. 37.):

but = (hyp.);

∴ = , a part equal to the whole, which is absurd.

∴ $\nparallel$ ; and in the same manner it can be demonstrated, that no other line except is || ; ∴ || .

Q. E. D.