Jawabanmu

2014-07-18T23:55:23+07:00
A ( 2,-2,1)
b ( 2,3,6)

|a| = √2²-2²+1² = √9 = 3
|b| = √2² + 3² + 6² = √49 = 7

Cosα = a.b / |a||b|
         = (2.2 + -2.3 + 1.6) / 3.7
          = 4 / 21
itu soalnya uda bener?