(1)1+1/4+1/9+1/16+1/25+・・・=π^2/6

(2)1+1/3^2+1/5^2+1/7^2+1/9^2+・・・=π^2/8

(3)1-1/3+1/5-1/7+1/9-・・・=π/4

＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝

(4)π=∫(-1,1)dx/(1-x^2)^1/2

(5)π/2=∫(-1,1)(1-x^2)^1/2dx

＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝

(6)(2π)^1/2=∫(-∞,∞)exp(-x^2/2)dx

＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝

(7)π=Σ1/16^k(4/(8k+1)-2/(8k+4)-1/(8k+5)-1/(8k+6))

＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝