Re: f(x,y) * f(y,z) = f(x,z)



On Sep 15, 11:47 pm, "Jon Slaughter" <Jon_Slaugh...@xxxxxxxxxxx>
wrote:
"Narasimham" <mathm...@xxxxxxxxxxx> wrote in message

news:1189877998.942637.181890@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

Find general solutions for f from f(x,y) * f(y,z) = f(x,z). Only the
division and some division based functions comes to mind, like f(u,v)
= u/v, (u/v)^2, log(u) / log(v) etc. So what is the fullest basis?
TIA.

Narasimham

well, an obvious solution is if f is separable. f(x,y) = g(x)/g(y), then

f(x,z) = g(x)/g(z)

for arbitrary g.

This sorta generalizes what you were getting at. I'm not sure about the most
general case though.

The chain rule of differentiation operates much the same way,dy/dx =
(dy/dt)/(dx/dt) etc. even at the level of differentials, so I thought
perhaps some ODEs for f can be set up.Also similar is the case for
implicit functions using partial derivatives. But not able to go any
further in an attempt even to formulate generalization.

Regards,
Narasimham

.



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