jika y = cos (3/x) , maka dy/dx = ...

y = cos(3/x)
misal u = 3/x =3x^(-1)
du/dx = -3x^(-2) = -3/x²

y = cos u
dy/du = -sin u
dy/du = -sin(3/x)

dy/dx = dy/du . du/dx
          = -sin(3/x) . -3/x²
          = 3/x² . sin(3/x)

y = cos (3/x) = cos (3x⁻¹)
dy/dx = -sin (3x⁻¹) (-3x⁻²)
          = 3 sin (3/x) / x²