i don't know how to solve those question

aib axb the angle between a &b 1 a = (- 3 , - 10,- 5 ) 6= (- 3,9,-10) 2 ) a = ( 2, 6, 1 ) b = (- 4, - 3, 0 ) 3 a = ( - 4, 9, - 8 1 b = ( 4, 1 , - 8 ) 4 ) a = ( - 5, 1 1 - 10 ) b = (0,-2, 3) 5 a = ( - 7, 0 1 - 2 1 6= ( 10,- 6, 0 ) 1) a = ( 1 12, 3 ) 6= ( 4, 5, 6 )