MHB Are Equal: $$\sin \alpha_nx - \sinh \alpha_nx$$

  • Thread starter Thread starter Dustinsfl
  • Start date Start date
AI Thread Summary
The discussion centers on the equality of the expressions involving sine and hyperbolic sine functions, specifically $\sin \alpha_nx - \sinh \alpha_nx$. It is noted that both expressions converge at every eigenvalue defined by the equation $\sin x \cosh x = \cos x \sinh x$ within the range [0,1]. A plot confirms their equivalence over this finite range, which is relevant for applications like beam length analysis. The equality holds under the condition that $\sin \alpha_n \cosh \alpha_n = \cos \alpha_n \sinh \alpha_n$. This establishes a clear relationship between the trigonometric and hyperbolic functions in the context discussed.
Dustinsfl
Messages
2,217
Reaction score
5
$$
\sin \alpha_nx - \sinh \alpha_nx - \frac{\sin \alpha_n + \sinh \alpha_n}{\cos\alpha_n + \cosh\alpha_n}(\cos \alpha_nx -
\cosh \alpha_nx) = \sin \alpha_nx - \sinh \alpha_nx - \frac{\sin \alpha_n - \sinh \alpha_n}{\cos\alpha_n - \cosh\alpha_n}(\cos \alpha_nx -
\cosh \alpha_nx)
$$

When I plotted them, they were the same but I was only looking at a finite range since I am considering a beam of length 1.

In the range [0,1], they converge at every eigenvalue which are defined by $\sin x\cosh x = \cos x\sinh x$
 
Last edited:
Mathematics news on Phys.org
dwsmith said:
$$
\sin \alpha_nx - \sinh \alpha_nx - \frac{\sin \alpha_n + \sinh \alpha_n}{\cos\alpha_n + \cosh\alpha_n}(\cos \alpha_nx -
\cosh \alpha_nx) = \sin \alpha_nx - \sinh \alpha_nx - \frac{\sin \alpha_n - \sinh \alpha_n}{\cos\alpha_n - \cosh\alpha_n}(\cos \alpha_nx -
\cosh \alpha_nx)
$$

When I plotted them, they were the same but I was only looking at a finite range since I am considering a beam of length 1.

In the range [0,1], they converge at every eigenvalue which are defined by $\sin x\cosh x = \cos x\sinh x$

Hi dwsmith, :)

You can show that,

\[\sin \alpha_n\cosh \alpha_n = \cos \alpha_n\sinh \alpha_n\]

\[\Rightarrow\frac{\sin \alpha_n - \sinh \alpha_n}{\cos\alpha_n - \cosh\alpha_n}=\frac{\sin \alpha_n + \sinh \alpha_n}{\cos\alpha_n + \cosh\alpha_n}\]

So both sides are equal provided, \(\sin \alpha_n\cosh \alpha_n = \cos \alpha_n\sinh \alpha_n\).

Kind Regards,
Sudharaka.
 
Suppose ,instead of the usual x,y coordinate system with an I basis vector along the x -axis and a corresponding j basis vector along the y-axis we instead have a different pair of basis vectors ,call them e and f along their respective axes. I have seen that this is an important subject in maths My question is what physical applications does such a model apply to? I am asking here because I have devoted quite a lot of time in the past to understanding convectors and the dual...
Insights auto threads is broken atm, so I'm manually creating these for new Insight articles. In Dirac’s Principles of Quantum Mechanics published in 1930 he introduced a “convenient notation” he referred to as a “delta function” which he treated as a continuum analog to the discrete Kronecker delta. The Kronecker delta is simply the indexed components of the identity operator in matrix algebra Source: https://www.physicsforums.com/insights/what-exactly-is-diracs-delta-function/ by...

Similar threads

Replies
2
Views
36K
Replies
2
Views
1K
Replies
4
Views
2K
Replies
1
Views
1K
Replies
3
Views
7K
Back
Top