Page:First six books of the elements of Euclid 1847 Byrne.djvu/54

20 NY two sides and  of a triangle  taken together are greater than the third side.



Produce, and make =  (pr. 3.); draw. Then because =  (const.),

= (pr. 5.)

∴ >  (ax. 9.)

∴  +  >  (pr. 19.)

and ∴ +  >. Q.E.D.