ƒ(x，y) = x + (y - 1)arcsin√(x/y)ƒ_x (x，y) = 1 + (y - 1) * 1/√(1 + x/y) * 1/y = 1 + (y - 1)/[√y√(y - x)]ƒ_x (x，1) = 1 + (1 - 1)/[√1√(1 - x)] = 1希望对你有所帮助 还望采纳~~
