题目[例18]设f(x )连续,试求下列函数的导数.-|||-(1)f(t)dt;-|||-(2) (int )_(0)^x(x-t)f(t)dt ;-|||-(3) (int )_(0)^xcos ((x-t))^2dt ;-|||-(4) (int )_(1)^2f(x+t)dt.题目解答答案