7 6 Mr. glen ie’s Proportions. 
cor. v. The fegments of the bafe are proportional 
to the fegments of the Tides, which are adjacent to 
them. 
PROPOSITION 11. 
Let there be any two right lines given . "There is an angle 
which ?nay be made by thefe lines ; fuch that if, from their 
extremities which do not meet , right lines be drawn to 
the alternate angles of rhombi defer ibed on them. , and re- 
ciprocally applied to them when produced ; and from the 
faid angle through the interfedlion of thefe lines , a right 
line be drawn to meet the right line joining the faid ex- 
tremities ; the fegments of this line made thereby, foall be 
refpeSiively equal to the adjacent fegments of the given 
lines . 
therefore, by converfion, ab : BCrrcA : ad. Again, becaufc ab : bc = bc : ce, 
by converfion ab : ac = bc : be : and by permutation ab : bc = ac : be. 
Therefore ac : bectac : ad. Therefore ad and be are equal. I fay, more- 
over, that each of the two equal lines ad, be, is a mean in proportion between 
the two cd, ce. For becaufe ba : ac^ac : cd, by divifion bc : ca~ ad : dc. 
Again, becaufe ba :bc=tbc : ce, converting and dividing bc : ca=ce : eb. 
Therefore, ce : ebz:ad : dc. E. D . s. horsljey, 
LET 
