计算圆周率

Pi = 4/1 - 4/3 + 4/5 - 4/7 + 4/9

   =4/1 + (-4/3) + 4/5 +(-4/7)

规律：分子不变，分母1、3、5、7、9

     每一项越来越小：最后一项对绝对值<0.0000001

     每一项目是正负交替：*-1

     每一项组成：符号、分子、分母

Math.ads

import  math
sum = 0
fh =1
fm = 1
i = 1
while math.fabs(4/fm)>0.0001:
    sum += fh * 4 / fm

    fh = fh *-1
    fm = fm +2
    i+=1
print("次数%d"%i)
print("pi的值：%f"%sum )