80 Wright’s Mathematical Papers. 
nated by N, placed before the corresponding angle of commutation ; 
and likewise place, or suppose to be placed, N, or the negative sign, 
before the bases, whose positions are denoted by N, after the corres- 
ponding angle of commutation. 
Make the factor in the third column, corresponding to the second 
side, equal to 0, and let the perpendicular belonging to the second 
be considered as the first factum resulting from the perpendiculars. 
Then perform the following operation, for each of the remaining 
sides. When its perpendicular and the next preceding factum have 
values of the same kind, take their sum, prefixing the negative sign 
' when they are negative; but when they have values of different — 
kinds, take their difference, placing the negative sign before it, when 
the greater number is negative. Then the factum thus obtained, 
and the base belonging to the side, will be factors, to be multiplied 
together. Again, observing the foregoing directions, take the sum, 
or difference, as the case may be, of the perpendicular and factum 
last obtained. Bring the several products, whose factors are AA or 
NN, into one sum, and the several products, whose factors are AN 
or NA, into another sum. Take the difference of these sums, half 
of which will be the required area of the polygon. 
Example 1. The same as in No. Il. 
Ang. LoS. B: Pee 
250 95. - 2500 
a or rs 
A.OA. 0.00 7.25 
25° 8 Bea Bes 
0.00 
N. 25 N. 43/88 wi Oe 
~ 25°27 18 18.00 
10.75 
A.ON. 0.00 28.75 
320 14.37 ees oie 
16.56 
N. 32 N. pall il 45 Ay 
123° 26 —23.56 
155 -4/ 9, 10 
N. 25 A. 10.99 —42.75 
AA. NN. AN. NA 
126.022 
210.898 
336.920 
168.460 
