
Kurt C. answered 03/20/19
Math, Science & Computer tutor
Start by calculating the derivative of xyz with respect to x.
d(xyz)/dx = yz ; y, z treated as constants
d(xyz) = yz dx ; multiply both sides by dx
∫d(xyz) = ∫yz dx ; integrate both sides
= yz ∫dx
= yzx = xyz
Alternatively, if x, y and z are functions of t. You can use the product rule to see that
d(xyz)/dt = xy * dz/dt + xz * dy/dt + yz * dx/dt
d(xyz) = xy*dz + xz*dy + yz*dx ; multiplying both sides by dt
∫d(xyz) = ∫xy*dz + ∫xz*dy + ∫yz*dx ; integrating both sides