已知y=x²sin(1/x),求dy/dx解:dy/dx=(x²)'sin(1/x)+x²[sin(1/x)]' =2xsin(1/x)+x²[cos(1/x)](1/x)' =2xsin(1/x)+x²[cos(1/x)](-1/x²) =2xsin(1/x)-cos(1/x)
y=x^2.sin(1/x)y' = x^2 cos(1/x) . ( -1/x^2) + 2xsin(1/x) = -cos(1/x) +2xsin(1/x)