108 The Inverse Method of Central Forces. 
» 
Ge ee, R a = additional force at the dis- 
2 
tance y, and the force in the first orbit at the same 
distance = —_, therefore the whole compound force 
-n ? FF? R z 
1 uk G? — ys Soe 
Kas EF Ei 
Cor, 9. If instead of ( 1), be supposed=force 
in the first orbit at the distance 1, it will easily ap- 
pear that the compound force in the other orbit, at 
La —F yet’ 
J) I 
F ‘ 
the same expression that is found after a very diffe- 
rent manner, Princip. book 1st, sect. gth. 
the distance y, will = “: 
