[ 2 45 3 
fin. P cof. A, the tables will give the angle B, and 
fin. P fin. A . . r . . , 
tan g-p— cof ' ~b* — » com P ut:atlC)n or which can 
give no trouble. Hence it appears, that the calculus 
for finding the true parallax is not more difficult than 
that, which gives the laid parallax with an error, the 
value of which is unknown ; for it is evident that the 
above computation for finding p " is only an approxi- 
mation, and that, to make it accurate, it would be ne- 
ceflary to carry it Hill on by finding fin. p"'z=z fin. P 
fin. (A -\-p"), and afterwards fin. p"" = P fin. 
( A -\-p" ) &c. 
§ 3. I therefore think myfelf in the right to prefer 
my method to that hitherto ufed by aftronomers. To 
confirm my opinion, I made a trial, by putting P— 59' 
and A=30°, and found 0^,43, in which 
the error of the ufual computation amounts to near 
half a fecond ; I therefore give the preference to the 
geometrical calculus. 
§ 4. Before I quit the formula tang. p~ 
fin., P fin. A j mu ft obferve, that the computation 
1 — fin. P cot. A 1 
of p may be executed by other methods to the fame 
exadtnefs. If we take cof. 2 C— fin. P cof. A, we 
fin. P fin. A 
{hall have tang. p~ o (f. n "c jT* an< ^ com p utatl on 
of this new formula is extremely eafy. 
- fin. P fin. A 
§5. The formula tang. p= 
hefides, fin .p~ — ; make fin. 
v' i+iin.P z — 2 fin. P cof. A 
P = 2 cof. D, D being a given angle, of which we 
may have tables ready made, and we fhall have fin. 
