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Thread: sin(x + y) + sin(x + 2y) + sin(x + 3y) +...+ sin(x + ny) ???

  1. #1 sin(x + y) + sin(x + 2y) + sin(x + 3y) +...+ sin(x + ny) ??? 
    Forum Freshman Sudhamsu's Avatar
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    What is [sin(x + y) + sin(x + 2y) + sin(x + 3y) +...+ sin(x + ny)] equal to?
    The angles are in arithmetic progression....

    Help required urgently!!


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  3. #2  
    Moderator Moderator
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    As this looks like homework, I urge you to read this


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  4. #3  
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    Then all you have to do is simplify the RHS and equate imaginary parts.
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  5. #4  
    Forum Junior Vroomfondel's Avatar
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    I'm impressed!
    I demand that my name may or may not be vroomfondel!
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  6. #5  
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    That’s pretty much the standard way of computing the sum of the sines or cosines of an arithmetic progression of angles.

    Another way is to use a telescoping formula – but for this you may need to be smart enough to find a formula that fits.
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  7. #6  
    Forum Junior Vroomfondel's Avatar
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    I know it's the standard way, but I expected it to take a few more lines than that. I'm going to try out the telescoping way now.
    I demand that my name may or may not be vroomfondel!
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