在x=0处是这样：sin(x) = x - x ^ 3 / 3!+ x ^ 5 / 5!- x ^ 7 / 7!+ x ^ 9 / 9!- x ^ 11 / 11!+...+(-1)^k*x^(2k-1)/(2k-1)!+o(x^(2k-1))cos(x)=1-x^2/2!+x^4/4!+...+(-1)^kx^2k/(2k)!+o(x^(2k))在x不等于0处就不是...