How do you resolve forces on an object on an angled plane?

The forces should be resolved in two directions: parallel to the plane, and perpendicular to the plane. Friction will act parallel to the plane (up the slope), and the normal force wil act perpendicular to the plane. The weight of the object will act vertically down, so it must be split into its components. The component acting perpendicular to the plane, in the opposite direction to the normal force, will be WcosA, where W is the weight of the object, and A is the angle of the incline of the plane. The component of the weight acting parallel to the plane (down the slope) will be WsinA. We can use the resolution of these forces to work out the coefficient of friction.