Question

Jawab no 7 dan 9 nya ya...

Answer 1

A•b= |a||b|cos(a,b)=3.4.cos60°= 12.1/2= 6
Misalkan |a-2b|=x
x^2= |a-2b|^2
= |a|^2 - 4a•b + |2b|^2
= 9-4.6+64
= 49
x= V49= 7
|a-2b|= 7 (C)

Answer 2

7. |a-2b| = √(|a|²+4|b|²-4|a|.|b|.cos 60)
              = √(9+(4.16)-(4.3.4.(1/2)))
              = √49
              = 7.............opsi C

9. proyeksi orthogonal A pada garis B:
    C = (a.b/|b|²).b
        = (30/45)(4i + 5j + 2k)
        = (8/3)i + (10/3)j + (4/3)k............opsi A