Can cosh(x)cosh(y) be rewritten in terms of k=Cosech(x)*Cosech(y)?

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Discussion Overview

The discussion revolves around the possibility of expressing the product of hyperbolic cosine functions, Cosh(x)*Cosh(y), solely in terms of the product of hyperbolic cosecant functions, k=Cosech(x)*Cosech(y). Participants explore the relationships between these hyperbolic functions and the implications of such a transformation.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions whether Cosh(x)*Cosh(y) can be rewritten in terms of k, indicating that the problem seems straightforward but has proven challenging.
  • Another participant suggests using the identity (cosh(t))^2 - (sinh(t))^2 = 1 to express cosh(t) and relates it to csch(t), proposing a potential pathway to the solution.
  • A different participant responds that the hint does not address their specific requirement to express Cosh(x)*Cosh(y) exclusively in terms of k, noting that it leads to terms like Sinh(x)+Sinh(y) instead.
  • One participant asserts that it is not possible to define a function f(k) that represents Cosh(x)*Cosh(y) in terms of k, providing examples where the same value of k leads to different outputs for the function, thus indicating that it cannot be a single-valued function.

Areas of Agreement / Disagreement

Participants express differing views on the possibility of rewriting Cosh(x)*Cosh(y) in terms of k. While some suggest methods to explore the relationship, others argue that such a transformation is not feasible, leading to an unresolved discussion.

Contextual Notes

The discussion highlights the complexity of hyperbolic functions and the challenges in establishing a direct relationship between Cosh and Cosech in this context. The examples provided illustrate the dependence on specific values and the resulting ambiguity in defining a function.

Who May Find This Useful

This discussion may be of interest to those studying hyperbolic functions, exploring mathematical relationships in advanced mathematics, or engaging in theoretical discussions in physics or engineering contexts.

emanuele.levi
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Given the quantity

Cosh(x)*Cosh(y)


where x and y are two indipendent real variables is it possible to write it only in function of


k=Cosech(x)*Cosech(y)

?
It could seem a quite easy problem but I spent a few days between the proprieties of hyperbolic functions and I really didn't find a way to solve it.
 
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Hint:
Use the identity (cosh(t))^2-(sinh(t))^2=1 to solve for cosh(t).

Then use the fact that csch(t) = 1/sinh(t) so sinh(t) = 1/csch(t).
 
thank you for the hint Russell,
but that's not a solution to my problem, as I want to write the quantity

Cosh(x)*Cosh(y)


ONLY in function of k. If I did like you suggested me, I find terms like


Sinh(x)+Sinh(y)


and I can't find a way to write them in function of k.
 
It is not possible.
Assume you have some function f(k) that represents cosh(x)cosh(y) in terms of k.
When k = 1/2, then what would f(k) be?

Let sinh(a)=.5, sinh(b)=4. Then k = 1/(.5*4) = 1/2
Then cosh(a)*cosh(b)=sqr( 1+1/4)*sqr( 1+16)=sqr(85/4)=f(1/2)


However look at:
let sinh(c)=1, sinh(d)=2. Then k = 1/(1*2) = 1/2
But cosh(a)*cosh(b)=sqr( 1+1)*sqr( 1+4)=sqr(10)=f(1/2)

So, f(1/2) would not have a single output value, it is not a function.
 

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