<Dd> R 2 = R ⋅ R = tr ⁡ (R R T), (\ displaystyle \ mathbf (R) ^ (2) = \ mathbf (R) \ cdot \ mathbf (R) = \ operatorname (tr) (\ mathbf (R) \ mathbf (R) ^ (T)),) </Dd> <P> where tr denotes the sum of the diagonal elements of the outer product matrix, known as its trace . </P>

How to find moment of inertia parallel axis theorem