sint=t-t^3/3!+t^5/5!-t^7/7!+t^9/9!-.+{(-1)^n}t^(2n-1)/(2n-1)!sint/t=1-t^2/3!+t^4/5!-t^6/7!+t^8/9!-.+{(-1)^n}t^(2n-2)/(2n-1)!然后求导=-t/(1!3)+t^3/(3!5)+.+{(-1)^n}t^(2n-3)/{(2n-1)(2n-3)!}