The moment of inertia of a rectangle about its own centroidal axis is given by:
where b = width parallel to c axis and h = height perpendicular to c axis.
Using this equation, the moments of inertia for shapes (1) and (2) about their own centroids can be computed. However, the moments of inertia for shapes (1) and (2) are needed about the z centroidal axis for the complete tee shape. To accomplish this, the parallel-axis theorem must be used.