why "symsum(sin(kpi)k,0,n)" not equal zero

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murat 2014-2-23

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回答： Walter Roberson 2014-2-23

why "symsum(sin(k*pi)*k,0,n)" not equal zero?

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Answer 1

Walter Roberson 2014-2-23

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在 MATLAB Online 中打开

symsum(sin(k*sym('pi'))*k,0,n)

Remember, "pi" in MATLAB is only a numeric approximation to the transcendental number; you need to use the transcendental number rather than the numeric approximation.

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Answer 2

Jan 2014-2-23

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What is n? For e.g. n=0.5 the result is not surprising.

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Answer 3

Paul 2014-2-23

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I don't think Matlab recognizes that sin(pi)= 0, therefore it cant simplify further sin(pi*n)*(n/2 + 1/4). Just type sin(pi) and you will see you won't get 0. sind(180) does give 0 but sind doesn't support symbolic variables.