Question 1: After general grading, we will find that the numerator and denominator tend to zero at the same time. For this 0/0 form of limit, L'H?pital's law can generally be used to get the answer. But if this problem is not a derivative, it will be a bit troublesome. The second question: similar to the first question, it is in the form of zero multiplied by infinity and cannot be directly replaced. Can be transformed into the first question and form. Let t= 1-x, then the original problem can be changed to LIMT * tan (π/2-π t/2) t→ 0 = LIMT/tan (π t/2) t→ 0 = 2/π.