The right hand side of Eq. (4.12) will directly provide the displacement of point C due to applied external forces. This method is also known as unit load method.
Similarly for finding out a rotation, at any point of a loaded structure, the corresponding Eq. (4.12) will take place as
(4.13)
where denotes the internal force in the members due to virtual unit moment applied in the direction of interested .
at any point of a loaded structure, the corresponding Eq. (4.12) will take place as 
denotes the internal force in the members due to virtual unit moment applied in the direction of interested 
. 
