Page:First six books of the elements of Euclid 1847 Byrne.djvu/69

Rh HE opposite sides and angles of any parallelogram are equal, and the diagonal divides it into two equal parts.



and common to the two triangles.

and =  (ax.):

Therefore the opposite sides and angles of the parallelogram are equal: and as the triangles and  are equal in every respect (pr. 4.), the diagonal divides the parallelogram into two equal parts.

Q. E. D.