This problem refers specifically to http://books.google.com/books?id=W9...ss components on an arbitrary plane"&f=false". The text comments that Area BOC = Projection of area ABC on the yz plane, and that this equals the area of ABC times the direction cosine in the x-direction of the normal vector to the plane, and so on for the other faces. Similarly, http://books.google.com/books?id=Gl...ss components on an arbitrary plane"&f=false" states that "it can be seen" that the ratio of areas Ax/A = nx, etc. I'm looking for a mathematical verification that this is true. Most likely because it is a math issue, the authors deemed the explanation unecessary in a solid mechanics text. My linear algebra background is pretty weak, so you may need to include some fundamentals in order for me to follow. Thanks in advance.