Theorem of parallel axis
It states that if the M.I. of plane area about the axis passing through the C.G. can be denoted by I_{G}. The M.I. of area about any other axis AB, parallel to 1^{st} and a distance 'h' from C.G. can be given by
I_{A}_{B} = I_{G} + a.h^{2}
Where;
I_{A}_{B} = M.I. of area about an axis AB _{I}_{G} = M.I. of area about its C.G.
a = Area of section
h = Distance between C.G. of section and axis AB
This formula gets reduced to;
I_{X}_{X } = IG + a.h^{2}; h = distance from x - axis i.e.; Y - y
I_{Y}_{Y} = IG + a.h^{2}; h = distance from y - axis i.e.; X - x