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How do you solve this equation? 

 

(1/(ex - e-x)) = 2 

 Oct 6, 2015

Best Answer 

 #3
avatar+26387 
+30

How do you solve this equation? 

\(\dfrac{1}{e^x - e^{-x}}= 2 \)

 

\(\begin{array}{rcl} \dfrac{1}{e^x - e^{-x}} &=& 2 \\ e^x - e^{-x} &=& \dfrac{1}{2} \qquad | \qquad \dfrac{e^x - e^{-x}}{2} = \sinh{(x)}\\ 2\sinh{(x)} &=& \dfrac{1}{2} \\ \sinh{(x)} &=& \dfrac{1}{4}\\ x &=& \text{arsinh}{ \left(\dfrac{1}{4} \right)} = \text{sinh}^{-1}{ \left(\dfrac{1}{4} \right)}\\ \mathbf{x} & \mathbf{=} & \mathbf{ 0.2474664615472692 } \end{array}\)

 

laugh

 Oct 7, 2015
 #1
avatar+118667 
+5

Come on Namadesto,

We have answered 2 of these questions for you in the last 12 hours.

How about you giving us some of your thoughts on how you might be able to solve it ?

We can talk those through with you if you like :)

 

Hint:  let y=e^x

 

You can simplify before or after you do the substitution.  :)

 Oct 6, 2015
edited by Melody  Oct 6, 2015
 #2
avatar+129845 
+10

(1/(ex - e-x)) = 2   

 

Notice that we can invert both sides and get :

 

(ex - e-x)  = 1/2     multiply through by 2ex  

 

2e2x - 2 = ex      subtract ex from both sides and rearrange

 

2e2x - ex - 2  = 0    this will not factor......let ex  = y   and we have

 

2y^2 - y - 2 = 0     and the solutions for this are....y ≈ -.78078     and y  = 1.2808

 

Therefore, ex = -.78078 (impossible).......  or ex = 1.2808

 

So

 

ex  =  1.2808     which means that x = ln 1.2808  = about .2475

 

 

cool cool cool

 Oct 6, 2015
 #3
avatar+26387 
+30
Best Answer

How do you solve this equation? 

\(\dfrac{1}{e^x - e^{-x}}= 2 \)

 

\(\begin{array}{rcl} \dfrac{1}{e^x - e^{-x}} &=& 2 \\ e^x - e^{-x} &=& \dfrac{1}{2} \qquad | \qquad \dfrac{e^x - e^{-x}}{2} = \sinh{(x)}\\ 2\sinh{(x)} &=& \dfrac{1}{2} \\ \sinh{(x)} &=& \dfrac{1}{4}\\ x &=& \text{arsinh}{ \left(\dfrac{1}{4} \right)} = \text{sinh}^{-1}{ \left(\dfrac{1}{4} \right)}\\ \mathbf{x} & \mathbf{=} & \mathbf{ 0.2474664615472692 } \end{array}\)

 

laugh

heureka Oct 7, 2015

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