question_answer 18)

Find the direction cosines of the vector joining the points A(1, 2, –3) and B(–1, –2, 1) directed from A to B.  

Answer:

Let  be the vector representing       = (?1, ?1)                      d? ratios of vector are ?2, ?4, 4,             cosines of vector       i.e.,                         ,             i.e.,       i.e.,