Describing a sum with a while loop

Question

Jonathan Larsson 2019-9-30

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评论： Steven Lord 2019-9-30

Hello I was woundering how you do this formula for pi as variable s in a while loop.

For example;

n=a big number

s=0

while s<=pi

s=s+n

end

Thanks!

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Answer 1

Bob Thompson 2019-9-30

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I'm pretty sure that adding a big number to 0 will bump you over pi on the first iteration, but maybe that's just me. I would do something more like the following:

s = 0;
tmp = 0;
k = 0;
while s<=pi
    k = k + 1;
    tmp = tmp + (-1/3)^k/(2*k+1);
    s = sqrt(12)*tmp;
end

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Steven Lord 2019-9-30

Of course, this approach assumes you know the answer you're trying to compute.

To approximate pi without actually knowing pi you probably want to loop until the step you're adding is "small enough" for some definition of "small enough".

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