This document discusses the principle of moments, which states that the moment of a force about a point is equal to the sum of the moments of its components about that point. It provides examples of calculating the moment of a force about different points using both trigonometric methods and resolving the force into Cartesian components. In one example, the moment of a 200N force acting at an angle is calculated to be 14.1 Nm about point A. In another, the moment of a 400N force is found to be -98.6 Nm about point O.