Mr. hutton’s Demonjirations , 8c c. ,6c 
THE DEMONSTRATION. 
. 
Parallel to one fide, af, of the polygon abcdef,^ 
through all the angular points, draw bh, ci, dk, el, 
fm. Then are the feveral angles, .which are made by 
thefe parallels and the adjacent fides of the figure, re- 
fpedtively equal to the fums of all the exteiior angles of 
the figure, from the beginning to the place of each 
angle; by the beginning is meant either extremity of 
the fide af. Thus the z_ nab = a, the a obc = + ft 
aicd -<x + /2 + y, the l. kde '= d +* /S + y ~ $ ( for ^ re 
being without the figure, is fubtraCted in fie ad o ein £ 
