Wrote

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I guess we can not use the same matrix of contour point to get the area and de center of mass ... Or am I wrong ?

Hola Manrique. If I'm not wrong, in the Martin's worksheet, the area is A(C) and the center of mass, which he call CG = [S.x(C)/A(C), S.y(C)/A(C)]

Best regards.
Alvaro.

You can try to use chunk() from PolyProperties. For a generic oriented line, you have to rotate the polygon using the line orientation, apply the chunk() function about an axis, and rotate back the polygon.