how do calculate send moment of area. here is the exampel. I do understand the way one calculate Ixx and Iyy and Ixy. the smaller part has thikness t and the biggest part 3t. I get : if you place global coordinate system on the top you will get the position of center of gravity to CG=(3a/8,-a/4). Now I do: define variable s which is the road Ixx=∫y²dA=∫t(s sin30)²ds=t[(S³/3)(1/4)]=ta³/12 and we do the same with the right part. and we will get 3ta³/12 Adding these two gives ta³/3. but in the solution they have (ta³/3)*(1/2)². I dont get where (1/2)² is comming from. This is not homework! This is an example from a exam!