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tan(2π/λ-λ/8)= tan π/4 How could this be correct; please explain.

 Sep 1, 2016

Best Answer 

 #1
avatar+118658 
+10

tan(2π/λ-λ/8)= tan π/4 How could this be correct; please explain.

 

There is more than one answer to this because tan pi/4 = tan 5pi/4 = tan 9pi/4 etc

 

The most basic answer is found by solving

 

\(\frac{2\pi}{\lambda}-\frac{\lambda}{8}=\frac{\pi}{4}\\ 8\lambda (\frac{2\pi}{\lambda}-\frac{\lambda}{8})=8\lambda(\frac{\pi}{4})\\ 16\pi-\lambda^2=2\pi \lambda\\ 0=\lambda^2+2\pi \lambda-16\pi\\ \lambda=\frac{-2\pi\pm \sqrt{4\pi^2 +64\pi}}{2}\\ \lambda=\frac{-2\pi\pm 2\sqrt{\pi^2 +16\pi}}{2}\\ \lambda=-\pi\pm \sqrt{\pi^2 +16\pi}\\\)

 

To get the general solution is the same method just the algebra is a bit worse

 

\(\frac{2\pi}{\lambda}-\frac{\lambda}{8}=\frac{\pi}{4}+\pi n \qquad n\in Z\\\)

andthen continue the same as the first one.    :)

 Sep 1, 2016
 #1
avatar+118658 
+10
Best Answer

tan(2π/λ-λ/8)= tan π/4 How could this be correct; please explain.

 

There is more than one answer to this because tan pi/4 = tan 5pi/4 = tan 9pi/4 etc

 

The most basic answer is found by solving

 

\(\frac{2\pi}{\lambda}-\frac{\lambda}{8}=\frac{\pi}{4}\\ 8\lambda (\frac{2\pi}{\lambda}-\frac{\lambda}{8})=8\lambda(\frac{\pi}{4})\\ 16\pi-\lambda^2=2\pi \lambda\\ 0=\lambda^2+2\pi \lambda-16\pi\\ \lambda=\frac{-2\pi\pm \sqrt{4\pi^2 +64\pi}}{2}\\ \lambda=\frac{-2\pi\pm 2\sqrt{\pi^2 +16\pi}}{2}\\ \lambda=-\pi\pm \sqrt{\pi^2 +16\pi}\\\)

 

To get the general solution is the same method just the algebra is a bit worse

 

\(\frac{2\pi}{\lambda}-\frac{\lambda}{8}=\frac{\pi}{4}+\pi n \qquad n\in Z\\\)

andthen continue the same as the first one.    :)

Melody Sep 1, 2016

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