A cantilever I beam has a cable at end B that supports a force is the position vector f...

A cantilever I beam has a cable at end B that supports a force is the position vector from end A of the beam to end B. Position vectors are parallel to the flange and web of the I beam, respectively. For determination of the internal forces in the beam (discussed in Chapter 8), and for mechanics of materials analysis, it is necessary to know the components of the force in the axial direction of the beam (AB) and in directions parallel to the web and flanges

Using the dot product, show that are orthogonal to one another.