$\displaystyle integral$(e^(-x²))...from there I went to e^(-x²)≡$\displaystyle sigma$[(-x²)^n/n!]=$\displaystyle sigma$[(-1)^n*x^(2n)/n!] so$\displaystyle integral$(e^(-x²))=$\displaystyle integral$[!]=$\displaystyle sigma$[(-1)^n*x^(2n)/n!] dx]...but I am stuck on where to go from here if there is route