Page:First six books of the elements of Euclid 1847 Byrne.djvu/50

16 F a side of a triangle is produced, the external angle  is greater than either of the internal remote angles ( or ).

Make =  (pr. 10.).

Draw and produce it until  = ; draw.

In and ;  =   =  and  =  (const. pr. 15),

∴ =  (pr. 4.),

∴ >

In like manner it can be shown, that if be produced,  >, and therefore

which is = is >.

Q.E.D.