How do you prove that #(x+pi/4)-(x+pi/4)^3/(3!)+(x+pi/4)^5/(5!)-... = 1-(x-pi/4)^2/(2!)+(x-pi/4)^4/(4!)=...= 1+x-x^2/(2!)-x^3/(3!)+x^4/(4!)+x^5/(5!)-..., x in (-oo, oo)?#