The symbols in the equations only represent the magnitudes (lengths) of the vectors.  If you remember, we represent the length of a vector by writing the vector symbol without the boldface type.  So

B = C X COS (58)

can be interpreted as saying "The length of B is equal to the length of C times the cosine of 58 degrees.   Writing the equation as

B = C X COS(58)

would be completely wrong, because it require that vectors B and C point in the same direction.