Page:First six books of the elements of Euclid 1847 Byrne.djvu/51

Rh NY two angles of a triangle are together less than two right angles.

Produce, then will

+ = But,  >  (pr. 16.)

∴ +  <, and in the same manner it may be shown that any other two angles of the triangle taken together are less than two right angles. Q.E.D.