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Pertanyaan

Diketahui sudut antara vektor x dan y ​ adalah 30°. Jika x ⋅ x = 6 dan x ⋅ y ​ = 21 , maka

Diketahui sudut antara vektor  dan  adalah 30°. Jika  dan , maka begin mathsize 14px style straight y with rightwards arrow on top times open parentheses straight x with rightwards arrow on top plus straight y with rightwards arrow on top close parentheses equals horizontal ellipsis end style 

  1. begin mathsize 14px style minus end style119

  2. undefined77

  3. 77undefined 

  4. 119undefined 

  5. 127undefined 

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Jawaban terverifikasi

Jawaban

jawaban yang tepat adalah D.

jawaban yang tepat adalah D.

Pembahasan

Karena maka Karena panjang vektor tidak mungkin negatif, maka Kemudian sudut antara vektor dan adalah . Sehingga Sehingga Dengan demikian, jawaban yang tepat adalah D.

Karena undefined  maka

begin mathsize 14px style table attributes columnalign right center left columnspacing 0px end attributes row cell straight x with rightwards arrow on top times straight x with rightwards arrow on top end cell equals 6 row cell open vertical bar straight x with rightwards arrow on top close vertical bar squared end cell equals 6 row cell open vertical bar straight x with rightwards arrow on top close vertical bar end cell equals cell plus-or-minus square root of 6 end cell end table end style 

Karena panjang vektor tidak mungkin negatif, maka begin mathsize 14px style open vertical bar straight x with rightwards arrow on top close vertical bar equals square root of 6 end style 

Kemudian sudut antara vektor undefined dan undefined adalah begin mathsize 14px style 30 degree end style. Sehingga

begin mathsize 14px style table attributes columnalign right center left columnspacing 0px end attributes row cell straight x with rightwards arrow on top times straight y with rightwards arrow on top end cell equals cell open vertical bar straight x with rightwards arrow on top close vertical bar open vertical bar straight y with rightwards arrow on top close vertical bar cos invisible function application 30 degree end cell row 21 equals cell square root of 6 times open vertical bar straight y with rightwards arrow on top close vertical bar times 1 half square root of 3 end cell row 21 equals cell 1 half square root of 18 times open vertical bar straight y with rightwards arrow on top close vertical bar end cell row 21 equals cell 3 over 2 square root of 2 times open vertical bar straight y with rightwards arrow on top close vertical bar end cell row cell open vertical bar straight y with rightwards arrow on top close vertical bar end cell equals cell fraction numerator 42 over denominator 3 square root of 2 end fraction end cell row cell open vertical bar straight y with rightwards arrow on top close vertical bar end cell equals cell fraction numerator 14 over denominator square root of 2 end fraction end cell row cell open vertical bar straight y with rightwards arrow on top close vertical bar end cell equals cell fraction numerator 14 over denominator square root of 2 end fraction times fraction numerator square root of 2 over denominator square root of 2 end fraction end cell row cell open vertical bar straight y with rightwards arrow on top close vertical bar end cell equals cell 7 square root of 2 end cell end table end style 

Sehingga

begin mathsize 14px style table attributes columnalign right center left columnspacing 0px end attributes row cell straight y with rightwards arrow on top times open parentheses straight x with rightwards arrow on top plus straight y with rightwards arrow on top close parentheses end cell equals cell straight y with rightwards arrow on top times straight x with rightwards arrow on top plus straight y with rightwards arrow on top times straight y with rightwards arrow on top end cell row blank equals cell straight x with rightwards arrow on top times straight y with rightwards arrow on top plus open vertical bar straight y with rightwards arrow on top close vertical bar squared end cell row blank equals cell 21 plus open parentheses 7 square root of 2 close parentheses squared end cell row blank equals cell 21 plus 98 end cell row blank equals 119 end table end style 

Dengan demikian, jawaban yang tepat adalah D.

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