Dear Sir,
The property to which I referred of the arcs of the hyperbola is in Chap. X. of the Trait¨¦ des Fonctions Elliptiques of M Legendre; 1 but I do not advance that this is identical with that which you offer.
Abel¡¯s theorem 2 is to be found p. 313 V.3 of Crelle¡¯s Journal, which affords the means of obtaining many results, similar to your theorem, and is I think worthy of your attention.
Your investigation of the property of the integrals under consideration shall I think embrace the determination of the constant and also the case when the hyperbola merges into two straight lines at right angles.
Making A = 1 as Legendre seems to do. The integral is 
Eqn 2 of M Legendres 2 Suppt p 163: may be written thus
Whence

I find ¦Ðx = pqr
but there is a difficulty with respect to the constant C.
Your equations however for pr, qr, pq are identical with those which are given by the preceding equation making x = p, x = q, & x = r successively.

putting for a1, c0 & c1 their values

which is your equation.
Are not P, Q & R each infinite?
I am, dear Sir Yours faithfully
J W Lubbock
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