Page:First six books of the elements of Euclid 1847 Byrne.djvu/43

Rh O bisect a given rectilinear angle.



Take =  (pr. 3.) draw, upon which describe  (pr. 1.), draw.

Because =  (const.) and  common to the two triangles and  =  (const.),

∴ =  (pr. 8.)

Q.E.D.