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 #1
avatar+118659 
0
Feb 6, 2017
 #3
avatar+118659 
0

I talked about this yesterday but my post disappeared. :(

 

I think that guests Wolfram Alpha input is incorrect.  

I have just copied and pasted guests input into Wolfram|Alpha and it was not entered correctly and Wolfram Alpha said it was equal to infinity...

https://www.wolframalpha.com/input/?i=sum_(n%3D2)%5E%E2%88%9E+(log((1+%2B+1%2Fn)%5En+(n+%2B+1)))%2F(log(n%5En)+log%5E(n+%2B+1)(n+%2B+1))

 

 

I put it into Wofram Alpha too.  

https://www.wolframalpha.com/input/?i=sum_(n%3D2)%5E%E2%88%9E+((log((1+%2B+1%2Fn)%5En+(n+%2B+1)))%2F(log(n%5En)+(log((n+%2B+1)%5E(n+%2B+1))))

 

I got no final answer but I was told that it was convergent and the graph indicated the answer was about 0.7  

(1/(2*log(2,e))) = 0.7213475204444817

So   It seemed that    1/(2ln2) is  likely to be the answer.

I personally have no idea how to do it though.  sad

 

I do not know how to do it :((

If you were a member then you would be able to private message Heureka or Alan (with the address of your question included) and ask them politely if they would be able to help you .:)

Feb 6, 2017
 #3
avatar+26388 
+5

sinx-2sinxcosx=0

 

Formula:

\(\begin{array}{|rcll|} \hline 2\ sin(x) \cos(x) &=& \sin(2x)\\ \hline \end{array}\)

 

 

So:

\(\begin{array}{|rcll|} \hline 0 &=& \sin(x) - 2\cdot sin(x) \cos(x) \quad & | \quad 2\cdot sin(x) \cos(x) = \sin(2x) \\ 0 &=& \sin(x) - \sin(2x) \quad & | \quad + \sin(2x) \\ \sin(2x) &=& \sin(x) \\ \hline \end{array} \)

 

First result:

\(\begin{array}{|rcll|} \hline \sin(2x) &=& \sin(x) \quad & | \quad \arcsin() \text{ both sides } \\ 2x &=& x \quad & | \quad -x \\ 2x-x &=& 0 \\ \mathbf{ x } & \mathbf{=} & \mathbf{ 0 \pm 360^{\circ} \cdot n } \quad & | \quad n \in N \\ \hline \end{array}\)

 

Second result:

\(\begin{array}{|rcll|} \hline \sin(2x) &=& \sin(x) \quad & | \quad \sin(x) = \sin(180^{\circ}-x) \\ \sin(2x) &=& \sin(180^{\circ}-x) \quad & | \quad \arcsin() \text{ both sides } \\ 2x &=& 180^{\circ}-x \quad & | \quad +x \\ 2x+x &=& 180^{\circ} \\ 3x &=& 180^{\circ} \quad & | \quad : 3 \\ x &=& 60^{\circ} \\ \mathbf{ x } & \mathbf{=} & \mathbf{ 60^{\circ} \pm 360^{\circ} \cdot n } \quad & | \quad n \in N \\ \hline \end{array}\)

 

Third result:

\(\begin{array}{|rcll|} \hline \sin(2x) &=& \sin(x) \quad & | \quad -\sin(x) = \sin(180^{\circ}+x) \\ \sin(2x) &=& -\sin(180^{\circ}+x) \\ \sin(2x) &=& \sin(-180^{\circ}-x) \quad & | \quad \arcsin() \text{ both sides } \\ 2x &=& -180^{\circ}-x \quad & | \quad +x \\ 2x+x &=& -180^{\circ} \\ 3x &=& -180^{\circ} \quad & | \quad : 3 \\ x &=& -60^{\circ} \\ \mathbf{ x } & \mathbf{=} & \mathbf{ -60^{\circ} \pm 360^{\circ} \cdot n } \quad & | \quad n \in N \\ \hline \end{array} \)

 

 

laugh

Feb 6, 2017

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