How Does the Limit of cosh and sinh Approach 1?

In summary: This leaves us with cosh(x) approaching e^x as x->infinity. Similarly, as x->infinity, e^x also approaches infinity. Therefore, we can say that lim(x-> infinity) cosh(x) = (lim x-> infinity)e^x. In summary, as T approaches 0, the expression of S becomes approximately equal to (mu*B)/(kB*T) due to the fact that both sinh(x) and cosh(x) approach e^x as x->infinity, making the 1 term negligible. This is also why the expression of ln(infinity) becomes equivalent to (mu*B)/(kB*T).
  • #1
thegirl
41
1
Hi I was wondering how you get this when taking the limit of T going to 0
Screen Shot 2016-03-30 at 16.44.47.png

From this expression of S:
Screen Shot 2016-03-30 at 16.49.30.png


Please help I don't see how ln infinity goes to uB/KbT (used u to represent the greek letter. And how does the other expression of sinh and cosh approach 1?
 
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  • #2
Both sinh(x) and cosh(x) approach e^x as x->infinity. Do you see why? So the 1 term becomes negligible compared to the cosh term. Does this help?
 
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  • #3
phyzguy said:
Both sinh(x) and cosh(x) approach e^x as x->infinity. Do you see why? So the 1 term becomes negligible compared to the cosh term. Does this help?
is that because when x aproaches infinity cosh(x) = infinity and as e^x also approaches infinity when x approaches infinity it can be said that lim(x-> infinity) cosh(x) = (lim x-> infinity)e^x? Also, thanks for replying!
 
  • #4
As ##T\rightarrow 0## we have that ##\ln{\left(1+2\cosh{\left(\frac{\mu B}{k_{B}T}\right)}\right)}\sim \ln{\left(1+ e^{\left(\frac{\mu B}{k_{B}T}\right)}\right)}\sim \frac{\mu B}{k_{B}T}## ...
 
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  • #5
thegirl said:
is that because when x aproaches infinity cosh(x) = infinity and as e^x also approaches infinity when x approaches infinity it can be said that lim(x-> infinity) cosh(x) = (lim x-> infinity)e^x? Also, thanks for replying!

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

As x->infinity the e^(-x) term approaches zero and becomes negligible compared to the e^x term.
 

Related to How Does the Limit of cosh and sinh Approach 1?

1. What is the limit of cosh and sinh?

The limit of cosh and sinh is infinity. This means that as the input approaches infinity, the output of both functions will also approach infinity.

2. What is the difference between cosh and sinh?

Cosh and sinh are two related hyperbolic functions. Cosh is the hyperbolic cosine function, while sinh is the hyperbolic sine function. The main difference between the two is that cosh is an even function, meaning it is symmetric about the y-axis, while sinh is an odd function, meaning it is symmetric about the origin.

3. How do you calculate the limit of cosh and sinh algebraically?

To calculate the limit of cosh and sinh algebraically, you can use the fact that cosh(x) = (e^x + e^-x)/2 and sinh(x) = (e^x - e^-x)/2. As x approaches infinity, e^x will become much larger than e^-x, so you can simplify the expressions to e^x/2 and e^x/2, respectively. Since e^x approaches infinity as x approaches infinity, the limit of both cosh and sinh will also be infinity.

4. What is the graph of cosh and sinh?

The graph of cosh and sinh are both hyperbolic functions, which means they have a similar shape to a parabola. However, while a parabola opens either upwards or downwards, the graph of cosh opens upwards and the graph of sinh opens downwards. Both graphs also have an asymptote at y=1, and approach infinity as x approaches infinity.

5. In what real-world applications are cosh and sinh used?

Cosh and sinh have various real-world applications, including in physics, engineering, and finance. They are often used to model the growth or decay of physical quantities, such as temperature or population. In finance, they are used to model the growth of investments or to calculate compound interest. They are also used in electrical engineering to model alternating current circuits.

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