Consider the vectors rightarrow a 4 rightarrow I rightarro
     Consider the vectors  rightarrow a  =  4 rightarrow I  +  rightarrow j  -  rightarrow k,  rightarrow b  =  - 4 rightarrow I  -  rightarrow j  +  rightarrow k,  rightarrow c  =  4 rightarrow I  -  rightarrow j  +  rightarrow k  rightarrow d  =  rightarrow I  +  rightarrow j  +  5 rightarrow k,  rightarrow g  =  -  rightarrow I  -  4 rightarrow j  +  rightarrow k.  Which pairs (if any ) of these vectors are  Are perpendicular?  (Enter none or  a pair or list of pairs, e.g., if rightarrow a is perpendicular to rightarrow b and rightarrow c, enter (a, b), (a, c).)  Are parallel?  (Enter none or a pair or list of pairs, e.g., if rightarrow a is perpendicular to rightarrow b and rightarrow c, enter (a, b), (a, c). )  Have an angles less than pi/2 between them?  (Enter none or a pair or list of pairs or a pair or list of pairs, e.g., if rightarrow a is perpendicular to rightarrow b and rightarrow c, enter (a, b), (a, c).)  Have an angle of more than pi / 2 between them ?  ( Enter none or a pair or list of pairs, i.g., if rightarrow a is perpendicular to rightarrow b and rightarrow c, enter (a, b), (a, c).) 
  
  Solution
Perpendicular a and d; b and d and d and g Parallel : a and b c ) a and c ; b and g ; c and d ; c and g d) a and g ; b and c ; b and g
