Exploring the Relationship between Cos(x) and Cosh(x): An Analysis of Identities

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In summary, cos(x) and cosh(x) are two trigonometric functions with different definitions, but they are closely related and often used in similar contexts. It is possible for cos(x) = cosh(x) to have infinite real solutions, and their domain is all real numbers. Cos(x) = cosh(x) is an even function and is commonly used in real-world applications in mathematics, physics, and engineering.
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contempquant
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Homework Statement





Homework Equations


from the identities found on the internet:

[tex]cos(x)=\frac{(e^{ix}+e^{-ix})}{2}[/tex]

and

[tex]cosh(x)=\frac{(e^{x}+e^{-x})}{2}[/tex]



The Attempt at a Solution



Assuming for the definition of cosh(x), if we take x as being equal to (ix), then surely this shows that cosh(x)=cos(x)? Can someone explain why this is wrong please? because i can't see it
 
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  • #2
It shows cosh(ix)=cos(x), not cosh(x)=cos(x). There's nothing wrong with that.
 

What is the difference between cos(x) and cosh(x)?

Cos(x) and cosh(x) are both trigonometric functions, but they are defined differently. Cos(x) is the cosine function, which is the ratio of the adjacent side to the hypotenuse in a right triangle. Cosh(x) is the hyperbolic cosine function, which is defined using exponential functions. While they may have different definitions, they are closely related and often used in similar contexts.

Can the equation cos(x) = cosh(x) have real solutions?

Yes, it is possible for cos(x) = cosh(x) to have real solutions. In fact, there are infinite real solutions for this equation. For example, x = 0 is a solution, as cos(0) = cosh(0) = 1. Other solutions can be found using trigonometric identities and algebraic manipulations.

What is the domain of the function cos(x) = cosh(x)?

The domain of cos(x) = cosh(x) is all real numbers. Both cosine and hyperbolic cosine functions are defined for any real input. However, if the equation is part of a larger problem or system, the domain may be restricted depending on the context.

Is cos(x) = cosh(x) an even or odd function?

Cos(x) = cosh(x) is an even function. This means that the graph of the function is symmetric about the y-axis. This can also be seen from the identities cos(-x) = cos(x) and cosh(-x) = cosh(x). Both sides of the equation will have the same value when x is replaced with -x.

How is cos(x) = cosh(x) used in real-world applications?

Cos(x) = cosh(x) is used in a variety of real-world applications, particularly in mathematics, physics, and engineering. For example, it is used in the calculation of electric fields in a conducting wire, as well as in the study of oscillations and waves. It is also used in the analysis of alternating current circuits and in the solution of differential equations.

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