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Gabarito Lista de exercícios - Vetores

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Geometria Anal´ıtica e A´lgebra Linear - GA21NB
Professor: Geovani Raulino
Gabarito Lista de Exerc´ıcios 05 - Vetores
1. (a) V
(b) F
(c) V
(d) V
(e) V
(f) V
(g) F
(h) V
(i) V
(j) V
(k) F
(l) V
(m) V
(n) V
(o) F
2. (a)
−→
OC +
−→
CH =
−→
OH =
−→
AE
(b)
−→
EH +
−→
FG =
−→
AO +
−→
OC =
−→
AC
(c) 2
−→
AE + 2
−→
AF =
−→
AD +
−→
DC =
−→
AC
(d)
−→
EH +
−→
EF =
−→
AO +
−→
OB =
−→
AB
(e)
−→
AO + 1
2
−→
BC =
−→
AO +
−→
OH =
−→
AH
(f)
−→
EO +
−→
BG =
−→
AF +
−→
FO =
−→
AO
(g) 2
−→
OE + 2
−→
OC =
−→
CD +
−→
AC =
−→
AC +
−→
CD =
−→
AD
(h) 1
2
−→
BC +
−→
EH =
−→
AE +
−→
EH =
−→
AH
(i)
−→
FE +
−→
FG =
−→
FG +
−→
FE =
−→
AO +
−→
OD =
−→
AD
(j)
−→
OG −
−→
HO =
−→
OG +
−→
OH =
−→
AF +
−→
FO =
−→
AO
(k)
−→
AF +
−→
FO +
−→
AO =
−→
AO +
−→
AO = 2
−→
AO =
−→
AC
(l)
−→
OG −
−→
HC −
−→
CG =
−→
OG +
−→
CH +
−→
GC =
−→
AF +
−→
FA +
−→
AE =
−→
AA +
−→
AE =
−→
AE
(m)
−→
DH +
−→
HG +
−→
GC =
−→
DG +
−→
GC =
−→
DC =
−→
AB
(n)
−→
FG +
−→
FE +
−→
HG =
−→
AO +
−→
OD +
−→
DO =
−→
AD +
−→
DO =
−→
AO
(o)
−→
DO +
−→
OH +
−→
FB =
−→
DH +
−→
FB =
−→
AF +
−→
FB =
−→
AB
3. (a) 120◦ (b) 120◦ (c) 60◦ (d) 60◦
4. Considere o triaˆngulo ABC como na figura onde M e N sa˜o os pontos me´dios de AB e AC,
respectivamente. Queremos provar que
−→
MN //
−→
BC, ou seja,
−→
MN = α
−→
BC, com α ∈ R.
Observe que, pela figura, temos
−→
MN =
−→
MA +
−→
AN =
1
2
−→
BA +
1
2
−→
AC
=
1
2
(
−→
BA +
−→
AC) =
1
2
−→
BC .
Portanto,
−→
MN //
−→
BC e ‖
−→
MN ‖ = 1
2
‖
−→
BC ‖.
5. (a) (3,-5) (b) (-5,4) (c) (1,−1
2
) (d) (13
2
,−9)
6. (a) −→x = (−15
2
, 15
2
) (b) −→x = (23
5
,−11
5
)
7. (a) (-4,1) (b) (2,5) (c) (-5,-30)
8. (a)
√
2
(b) 5
(c) 10
(d)
√
13
(e) 2
√
13
(f) 1
9. m = 3 ou m = −13
5
10. −→v = (−6, 3,−9)
11. (a) 2 (b) 38 (c) 4 (d) -181
12.
−→
AB · −−→BC = 0
13. α = -5
14. (a) 120◦ (b) 150◦
15. m = 3 ou m = -6
16. (a)
(
8
9
,−4
9
,−8
9
)
(b)
(
−6
5
, 0,−2
5
)
17. ~x = (1, 0, 1)
18.
−→
AB ×−→AC = (12,−3, 10)
19. ~u.~v = 5 ou −5.
20. Ap = 3
√
10.

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