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Diketahui vektor – vektor u = 9 i + a j ​ + b k dan v = a i − b j ​ + a k . Sudut antara vektor u dan vektor v adalah θ dengan cos θ = 11 6 ​ . Proyeksi pada adalah p ​ = 4 i − 2 j ​ + 4 k . Nilai b adalah ....

Diketahui vektor – vektor  dan . Sudut antara vektor  dan vektor  adalah  dengan . Proyeksi begin mathsize 14px style straight u end style pada begin mathsize 14px style straight v end style adalah . Nilai b adalah ....

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Jawaban terverifikasi

Jawaban

jawaban yang tepat adalah D.

jawaban yang tepat adalah D.space space  

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Pembahasan

Perhatikan bahwa Kemudian Proyeksi pada adalah , berarti Subtitusi persamaan (1) ke persamaan (3) Subitusi persamaan (4) dan (1) ke persamaan (2) : Jadi, nilai b adalah . Jadi, jawaban yang tepat adalah D.

Perhatikan bahwa

begin mathsize 14px style table attributes columnalign right center left columnspacing 0px end attributes row cell straight u with rightwards arrow on top. straight v with rightwards arrow on top end cell equals cell open parentheses table row 9 row straight a row straight b end table close parentheses open parentheses table row straight a row cell negative straight b end cell row straight a end table close parentheses end cell row cell straight u with rightwards arrow on top. straight v with rightwards arrow on top end cell equals cell 9 straight a minus ab plus ab end cell row cell straight u with rightwards arrow on top. straight v with rightwards arrow on top end cell equals cell 9 straight a horizontal ellipsis horizontal ellipsis horizontal ellipsis open parentheses 1 close parentheses end cell end table end style  

Kemudian

begin mathsize 14px style table attributes columnalign right center left columnspacing 0px end attributes row cell blank straight u with rightwards arrow on top. straight v with rightwards arrow on top end cell equals cell open vertical bar straight u with rightwards arrow on top close vertical bar open vertical bar straight v with rightwards arrow on top close vertical bar cos invisible function application straight theta end cell row cell straight u with rightwards arrow on top. straight v with rightwards arrow on top end cell equals cell square root of 9 squared plus straight a squared plus straight b squared end root square root of straight a squared plus open parentheses negative straight b close parentheses squared plus straight a squared end root open parentheses 6 over 11 close parentheses end cell row cell straight u with rightwards arrow on top. straight v with rightwards arrow on top end cell equals cell square root of 9 squared plus straight a squared plus straight b squared end root square root of straight a squared plus straight b squared plus straight a squared end root open parentheses 6 over 11 close parentheses horizontal ellipsis horizontal ellipsis horizontal ellipsis open parentheses 2 close parentheses end cell end table end style 

Proyeksi begin mathsize 14px style straight u end style pada begin mathsize 14px style straight v end style adalah begin mathsize 14px style straight p with rightwards arrow on top equals 4 straight i with rightwards arrow on top minus 2 straight j with rightwards arrow on top plus 4 straight k with rightwards arrow on top end style, berarti

begin mathsize 14px style table attributes columnalign right center left columnspacing 0px end attributes row cell fraction numerator straight u with rightwards arrow on top. straight v with rightwards arrow on top over denominator open vertical bar straight v with rightwards arrow on top close vertical bar end fraction end cell equals cell square root of 4 squared plus open parentheses negative 2 close parentheses squared plus 4 squared end root end cell row cell fraction numerator straight u with rightwards arrow on top. straight v with rightwards arrow on top over denominator square root of straight a squared plus straight b squared plus straight a squared end root end fraction end cell equals 6 row cell straight u with rightwards arrow on top. straight v with rightwards arrow on top end cell equals cell 6 open parentheses square root of straight a squared plus straight b squared plus straight a squared end root close parentheses horizontal ellipsis horizontal ellipsis horizontal ellipsis open parentheses 3 close parentheses end cell end table end style 

Subtitusi persamaan (1) ke persamaan (3)

begin mathsize 14px style table attributes columnalign right center left columnspacing 0px end attributes row cell 9 straight a end cell equals cell 6 open parentheses square root of straight a squared plus straight b squared plus straight a squared end root close parentheses end cell row cell 3 over 2 straight a end cell equals cell square root of straight a squared plus straight b squared plus straight a squared end root end cell row cell 9 over 4 straight a squared end cell equals cell straight a squared plus straight b squared plus straight a squared end cell row cell 1 fourth straight a squared end cell equals cell straight b squared end cell row cell straight a squared end cell equals cell 4 straight b squared end cell row straight a equals cell 2 straight b horizontal ellipsis horizontal ellipsis horizontal ellipsis open parentheses 4 close parentheses end cell end table end style 

Subitusi persamaan (4) dan (1) ke persamaan (2) :

begin mathsize 14px style table attributes columnalign right center left columnspacing 0px end attributes row cell 9 open parentheses 2 straight b close parentheses end cell equals cell square root of 9 squared plus 4 straight b squared plus straight b squared end root square root of 4 straight b squared plus straight b squared plus 4 straight b squared end root open parentheses 6 over 11 close parentheses end cell row cell 18 straight b end cell equals cell square root of 81 plus 5 straight b squared end root open parentheses 3 straight b close parentheses open parentheses 6 over 11 close parentheses end cell row cell fraction numerator 18 straight b over denominator 3 straight b end fraction open parentheses 11 over 6 close parentheses end cell equals cell square root of 81 plus 5 straight b squared end root end cell row 11 equals cell square root of 81 plus 5 straight b squared end root end cell row 121 equals cell 81 plus 5 straight b squared end cell row cell 5 straight b squared end cell equals 40 row cell straight b squared end cell equals 8 row straight b equals cell plus-or-minus 2 square root of 2 end cell end table end style 

Jadi, nilai b adalah begin mathsize 14px style plus-or-minus 2 square root of 2 end style

Jadi, jawaban yang tepat adalah D.space space  

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