MATLAB: Finding the sum of a series without symsum

mathematicssum

I'm trying to do the system sum of this equation, but all I've found is the command symsum to do this. However, I don't have the toolbar that this command comes with. Is there any way to either use this command or any other commands I can use to do this?
This is what I got so far. Any help is appreciated.
com_cos = symsum((((-1) ^ k) * x_val ^ (2 * k)) / factorial(2 * k), k = 1..Infinity);

Best Answer

You don't need 'symsum' to evaluate that series. It's easy to see that its sum is
com_cos = cos(x_val)-1
just by inspection.
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