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An Introduction to 
Generalized Calculus
Unit II - Generalized Calculus
Section B - Iterations from Anti-Iterations
  

I. Generalized Calculus

B. Iterations from Anti-Iterations

Deriving the Continued Product from the AP

In Unit I, Section III, the anti-product iteration was computed from the continuous product iteration. In essence, half of the Fundamental Therom of Product Calculus was derived:

q [ (continuous product) f(x) dx ] 1/dx = f(x).

Now, we will do the reverse, compute the iteration from the anti-product limit, and show that:

(continuous product) [qf(x)1/dx] dx = f(x) c. (constant c).

recall qf(x)1/d = [f(x+d)/f(x)]1/d = [f(x)/f(x-d)]1/d (as d-->0)

when we multiply qf(x)1/d qf(x-d)1/d, the f(x-d)1/d terms cancel:
f(x)1/d 
f(x-d)1/d 
f(x-d)1/d 
f(x-2d)1/d 
= f(x)1/d 
f(x-2d))1/d
with qf(x)1/d qf(x-d)1/d qf(x-2d)1/d ... qf(f -1(1))1/d, many more intermdediates cancel:
f(x)1/dx 
f(x-d)1/d 
f(x-d)1/d 
f(x-2d)1/d 
(x-d)1/d 
f(x-2d)1/d
... (f -1(1)+d)1/d 
f(f-1(1))1/d
= f(x)1/d 
f(f-1(1))1/d
The expansion on the left is equivalent to the continuous product

   x
=(continuous product) qf(x)1/d
   f -1(1)

The specific f -1(1) limit was chosen because at this point, f(f-1(1)) = 1, and the right, expansion result above simplifies to:

[f(x)/f(f -1(1))]1/d = f(x)1/d. Therefore, appending the right side to the left yields:

x
(continuous product) qf(x)1/d = f(x)1/d.
f -1(1)

x
(continuous product) [qf(x)1/d] d = f(x)1/d. (raise both sides to the dth power to get the origional equation.)
f -1(1)

Since (continuous product)(a..x) g(x)dx(continuous product) (a..s) g(x)dx(continuous product) (s..x) g(x)dx = c (continuous product) (s..x) g(x)dx = c(continuous product) g(x)dx  for some constant c,

(continuous product) [qf(x)1/d] d
f -1(1)
c(continuous product) [qf(x)1/dx]dx 

The 2nd Derivative

Recall from the last section,
d2f(x)/dx2 = [ f(x+2dx) - 2f(x+dx) + f(x) ] / d2.

A double integral could be performed to get the inverse, but, instead, a method similar to the above will be taken:

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