MATLAB: Sum of alternating series

series

How do you find the sum of a series with alternate signs. I know how to find with same signs but not alternating. I have no idea where to start. For example, 1-(1/3)+(1/5)-(1/7)+(1/9)…-(1/1003) with the sum equaling to 0.7849~pi/4
*This is not a homework problem. This is a studying question for my upcoming exam. I am very new to matlab and do not know where to start.

Best Answer

Just create the series and use the sum function: 
N = 1003;
frc = (1./(1:2:N));
exv = (-1).^(0:numel(frc)-1);
ser = frc.*exv
ser_sum = sum(ser)
ser_sum =
   0.784900155923366
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