The derivative function f '(x) of function f (x) is continuous, and f (0) = 0, f' (0) = A. note that the nearest point of curve y = f (x) and P (T, 0) is Q (s, f (s)), and find the limit value Lim s / T (when t tends to 0)

The derivative function f '(x) of function f (x) is continuous, and f (0) = 0, f' (0) = A. note that the nearest point of curve y = f (x) and P (T, 0) is Q (s, f (s)), and find the limit value Lim s / T (when t tends to 0)

First of all, from F (0) = 0, O (0,0) on the curve, and Q is the closest point on the curve to P, with PQ ≤ Po = | t |. Then | S-T | ≤ PQ ≤| t |, with | s | ≤ 2 | t |. When t tends to 0, s also tends to 0. (x, f (x)) to the square of P distance is (x-t)