Transformation of stresses in beer and johnston mechanics of materials. While reading the section on trsnformation of stresses they have solved by using the force components in x' and y' directions. I have attached a screenshot of the relevant page and the figure. I have few doubt as to how the force components in the x direction are resolved as shown in the book. When i tried resolving the forces in x' and y' direction i am not getting the solution as in the book but a totally differnt solution. using the pythagoras theorem to determine the resolved forces. Could someone please help me out as to how the answer in the book is done?