Summing parts of an array??

I have the following lines of code:

D=(8./(TSR.*9)).*(F.*(sin(relative_wind).^2).*(cos(relative_wind)-((TSR_local).*(sin(relative_wind)))).*(sin(relative_wind)+((TSR_local).*(cos(relative_wind)))).*(1-(Cd./Cl).*cot(relative_wind)).*(TSR_local.^2));
Cp=sum(D);

D is a 9x1 array. However I only want to sum the first 8 values in the array. Could anybody please show me how to do this as my current code is summing all 9 values?

Answer 1

[Azzi Abdelmalek]

sum(D(1:8))