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Pertanyaan

Sudut antara vektor a dan b sama dengan = 15 0 ∘ . Jika ∣ ∣ ​ b ∣ ∣ ​ = 6 dan a . b = − 9 maka a . ( b − a ) = ...

Sudut antara vektor  dan  sama dengan . Jika  dan  maka   

  1. negative 15 

  2. negative 12 

  3. negative 9 plus square root of 3 

  4. negative 6 

  5. negative 3 

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R. Hajrianti

Master Teacher

Mahasiswa/Alumni Universitas Pendidikan Indonesia

Jawaban terverifikasi

Jawaban

jawaban yang tepat adalah B.

jawaban yang tepat adalah B.

Pembahasan

Diketahui: (sudut antara vektor dan ) Ingat! Perkalian skalar vektor dengan vektor didefinisikan sebagai hasil kali panjang vektor dan panjang vektor dengan kosinus sudut yang diapit oleh vektor dan vektor atau . Maka: Sehingga: Jadi, jawaban yang tepat adalah B.

Diketahui:

  • alpha equals 150 degree (sudut antara vektor a with rightwards arrow on top dan b with rightwards arrow on top)
  • open vertical bar b with bar on top close vertical bar equals 6
  • a. b equals negative 9 

Ingat!

  • Perkalian skalar vektor a with rightwards arrow on top dengan vektor b with rightwards arrow on top open parentheses table attributes columnalign right center left columnspacing 0px end attributes row blank blank cell a with rightwards arrow on top end cell end table table attributes columnalign right center left columnspacing 0px end attributes row blank blank. end table table attributes columnalign right center left columnspacing 0px end attributes row blank blank cell b with rightwards arrow on top end cell end table close parentheses didefinisikan sebagai hasil kali panjang vektor a with rightwards arrow on top dan panjang vektor b with rightwards arrow on top dengan kosinus sudut yang diapit oleh vektor a with rightwards arrow on top dan vektor b with rightwards arrow on top atau table attributes columnalign right center left columnspacing 0px end attributes row blank blank cell a with rightwards arrow on top end cell end table table attributes columnalign right center left columnspacing 0px end attributes row blank blank. end table table attributes columnalign right center left columnspacing 0px end attributes row blank blank cell b with rightwards arrow on top end cell end table table attributes columnalign right center left columnspacing 0px end attributes row blank equals blank end table table attributes columnalign right center left columnspacing 0px end attributes row blank blank cell stack open vertical bar a close vertical bar with rightwards arrow on top end cell end table table attributes columnalign right center left columnspacing 0px end attributes row blank blank cell open vertical bar b with rightwards arrow on top close vertical bar end cell end table table attributes columnalign right center left columnspacing 0px end attributes row blank blank space end table table attributes columnalign right center left columnspacing 0px end attributes row blank blank cos end table table attributes columnalign right center left columnspacing 0px end attributes row blank blank space end table table attributes columnalign right center left columnspacing 0px end attributes row blank blank alpha end table.
  • a with rightwards arrow on top. a with rightwards arrow on top equals open vertical bar a with rightwards arrow on top close vertical bar squared 

Maka:

table attributes columnalign right center left columnspacing 0px end attributes row cell a with rightwards arrow on top. b with rightwards arrow on top end cell equals cell open vertical bar a with rightwards arrow on top close vertical bar open vertical bar b with rightwards arrow on top close vertical bar space cos space alpha end cell row cell negative 9 end cell equals cell open vertical bar a with rightwards arrow on top close vertical bar cross times 6 cross times cos space 150 degree end cell row cell negative 9 end cell equals cell open vertical bar a with rightwards arrow on top close vertical bar cross times 6 cross times open parentheses negative 1 half square root of 3 close parentheses end cell row cell negative 9 end cell equals cell open vertical bar a with rightwards arrow on top close vertical bar cross times open parentheses negative 3 square root of 3 close parentheses end cell row cell open vertical bar a with rightwards arrow on top close vertical bar end cell equals cell fraction numerator negative 9 over denominator negative 3 square root of 3 end fraction end cell row cell open vertical bar a with rightwards arrow on top close vertical bar end cell equals cell fraction numerator 3 over denominator square root of 3 end fraction cross times fraction numerator square root of 3 over denominator square root of 3 end fraction end cell row cell open vertical bar a with rightwards arrow on top close vertical bar end cell equals cell square root of 3 space satuan space panjang end cell end table 

Sehingga:

 table attributes columnalign right center left columnspacing 0px end attributes row cell a with rightwards arrow on top. left parenthesis b with rightwards arrow on top minus a with rightwards arrow on top right parenthesis end cell equals cell a with rightwards arrow on top. b with rightwards arrow on top minus a with rightwards arrow on top. a with rightwards arrow on top end cell row blank equals cell a with rightwards arrow on top. b with rightwards arrow on top minus open vertical bar a with rightwards arrow on top close vertical bar squared end cell row blank equals cell negative 9 minus open parentheses square root of 3 close parentheses squared end cell row blank equals cell negative 9 minus 3 end cell row blank equals cell negative 12 end cell end table 

Jadi, jawaban yang tepat adalah B.

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