Mohon bantuan nya teman teman

jawab

|a| = √(4 +16+16) = 6
|b| = √(9+4+36) = 7

a. b = 2(-3) - 4(2) +4(6) = 10

cos α = (a.b)/ |a||b|
cos α  = 10/42 = 5/21