PPT Slide
If the two directions are perpendicular, their dot product is zero; and the same is true for a direction that is contained in a plane.
From Equation 6.1, it is possible to obtain the and terms for all desired crystallographic directions of a crystal.
For instance, if the loading directions is [123] for an FCC crystal, then the Schmid factors of the various slip systems are found by obtaining the angles of [123] with > (perpendicular to slip planes) and [123] with (110) (in slip directions).