This document discusses Lami's theorem and provides an example. It begins by introducing the topic of mechanics of solids and listing the group members and their enrollment numbers. It then defines different types of force systems including coplanar, non-coplanar, concurrent, parallel, and general systems of forces. The document explains the triangle and polygonal laws for graphical conditions of equilibrium. It states the conditions of equilibrium for concurrent forces as the sum of forces in the x and y directions equaling zero, or the sum of moments equaling zero. Lami's theorem is then introduced as stating that if a particle is in equilibrium under three forces, each force bears the same proportionality to the sine of the angle between the