while loop doesn't produce correct result

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Jimmy W
Jimmy W 2017-4-12
评论： James Tursa 2017-4-12
sum = 0;
n = 0;
C = (2/(pi*(1-4*n^2)))^2;
while sum < (1/2)*0.99
n = n+1;
sum = sum + C;
end
disp(['number of terms:',num2str(n),'sum',num2str(sum)])
These are my codes. I want matlab to keep calculating until sum is greater than 99% of a half. However it stops at the first calculation and the result is clearly wrong. Any help would be greatly appreciated! Thanks!

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Roger Stafford
Roger Stafford 2017-4-12
You have not placed the line "C = (2/(pi*(1-4*n^2)))^2;" inside the 'while' loop where it could be updated with changing values of 'n', so 'C' stays constant. That will produce erroneous computation for you.
  2 个评论
Jimmy W
Jimmy W 2017-4-12
If I put the C line in the loop, it never stops calculating. The equation is always positive so at some point the sum should reach the target value. Is there anything else that I have done wrong?
James Tursa
James Tursa 2017-4-12
C get small rather quickly, so the sum never even gets close to 1/2.

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