[ 434 ] 
Problem XIII. 
3 6. Po find the nutation of the earth's axe caufed by 
the moon , during the time of a J'e mi -revolution oj the 
pole of the moon’s orbit , that is , in years. 
By Art. 23. x x (i- 
* OC OC ] • ^ t 1 
x — \ is to— , as the angle 
of the preceflion, found in the preceding Problem for 
fi < y 
the time — of the femi-revolution of the pole of the 
lunar orbit, is to the nutation during the fame time. 
By it, therefore, may be found the nutation, having 
the quantity of the preceflion of the preceding Prob. 
or, reciprocally, knowing the nutation during the time 
of a femi-revolution of the pole of the lunar orbit, 
the precefbon will be known to a geometrical cer- 
tainty, for the fame time. The ratio, in numbers, is 
IQ 9579 8 
6 1 236 
37. But we may alfo know the nutation during the 
time of a femi-revolution of the pole of the lunar or- 
nP 
bit, by the formula of Art. 22. which is B x — x 
ff 
— x jc ; which, without alteration, may be multiplied 
(* c 
, aw , a 7 r 
by — , or by 
Utt 21 
fince x, which is the ratio of the 
a x- 
7 
circumference to the diameter, is 
22 
7 
and we fhall 
nave 
