Cremona diagram

The method was developed by the Italian mathematician Luigi Cremona.

However, recognizable Cremona diagrams appeared as early as 1725, in Pierre Varignon's posthumously published work, Nouvelle Méchanique ou Statique.

[1] In the Cremona method, first the external forces and reactions are drawn (to scale) forming a vertical line in the lower right side of the picture.

This is the sum of all the force vectors and is equal to zero as there is mechanical equilibrium.

The same steps can be taken for joints D, H and E resulting in the complete Cremona diagram where the internal forces in all members are known.