π=4∫「0 to 1」dx/(1+x^2)
>(4/12)*(1/(1+(1/12)^2)+1/(1+(2/12)^2)+1/(1+(3/12)^2)+1/(1+(4/12)^2)+1/(1+(5/12)^2)+1/(1+(6/12)^2)+1/(1+(7/12)^2)+1/(1+(8/12)^2)+1/(1+(9/12)^2)+1/(1+(10/12)^2)+1/(1+(11/12)^2)+1/(1+(12/12)^2))
>3.0571