Write the law of conservation of angular momentum.

Explanation

The time rate of the total angular momentum of a system of particles about a point (taken as the origin of frame of reference) is equal to the sum of the external torque
`therefore (dvecL)/(dt)=vectau_(("ext"))`
If `vectau_(("ext"))=0" then "(dvecL)/(dt)=0`
`therefore dvecL=0`,so `vecL` = constant
Law of conservation of angular momentum :
..If the resultant external torque on the system is zero, then its angular moment remains constant...
Here `vecL` = constant, is equivalent to three scalar equations
`L_(x)=K_(1),L_(y)=K_(2)andL_(z)=K_(3)`
Here `K_(1),K_(2)andK_(3)` are constant, `L_(x),L_(y)andL_(z)` are the components of the total angular momentum `vecL` along X, Y and Z axes respectively.
The total angular momentum is conserved means that each of these components is conserved.