why "symsum(si​n(k*pi)*k,​0,n)" not equal zero

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

Answer 1

[Walter Roberson]

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.

Answer 2

[Jan]

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

Answer 3

[Paul]

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.