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Pertanyaan

Diketahui △ ABC dengan AC = 12 cm , BC = 8 cm , dan ∠ ACB = 12 0 ∘ . Tentukan: a. Panjang sisi AB b. sin ∠ ABC

Diketahui  dengan , dan . Tentukan:

a. Panjang sisi AB

b.

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S. Ayu

Master Teacher

Mahasiswa/Alumni Universitas Muhammadiyah Prof. DR. Hamka

Jawaban terverifikasi

Pembahasan

a. Panjang sisi AB Dengan menggunakan aturan cosinus, diperoleh: Maka, panjang sisi AB adalah . b. Dengan menggunakan aturan sinus, diperoleh: Maka, adalah .

a. Panjang sisi AB

Dengan menggunakan aturan cosinus, diperoleh:

table attributes columnalign right center left columnspacing 0px end attributes row cell AB squared end cell equals cell AC squared plus BC squared minus 2 times AC times BC times cos space angle ACB end cell row cell AB squared end cell equals cell 12 squared plus 8 squared minus 2 times 12 times 8 space cos space 120 degree end cell row cell AB squared end cell equals cell 144 plus 64 minus 192 times open parentheses negative 1 half close parentheses end cell row cell AB squared end cell equals cell 208 minus open parentheses negative 96 close parentheses end cell row cell AB squared end cell equals cell 208 plus 96 end cell row cell AB squared end cell equals 304 row AB equals cell plus-or-minus square root of 304 end cell row AB equals cell plus-or-minus 4 square root of 19 end cell row AB equals cell 4 square root of 19 space cm end cell end table

Maka, panjang sisi AB adalah 4 square root of 19 space cm.

 

b. sin space angle ABC

Dengan menggunakan aturan sinus, diperoleh:

table attributes columnalign right center left columnspacing 0px end attributes row cell fraction numerator sin space angle ABC over denominator AC end fraction end cell equals cell fraction numerator sin space angle ACB over denominator AB end fraction end cell row cell fraction numerator sin space angle ABC over denominator 12 space cm end fraction end cell equals cell fraction numerator sin space 120 degree over denominator 4 square root of 19 space cm end fraction end cell row cell sin space angle ABC end cell equals cell fraction numerator 12 space cm times sin space 120 degree over denominator 4 square root of 19 space cm end fraction end cell row cell sin space angle ABC end cell equals cell fraction numerator 12 space cm times begin display style fraction numerator square root of 3 over denominator 2 end fraction end style over denominator 4 square root of 19 space cm end fraction end cell row cell sin space angle ABC end cell equals cell fraction numerator 6 square root of 3 space cm over denominator 4 square root of 19 space cm end fraction end cell row cell sin space angle ABC end cell equals cell fraction numerator 6 square root of 3 over denominator 4 square root of 19 end fraction times fraction numerator square root of 19 over denominator square root of 19 end fraction end cell row cell sin space angle ABC end cell equals cell fraction numerator 6 square root of 57 over denominator 4 times 19 end fraction end cell row cell sin space angle ABC end cell equals cell fraction numerator 6 square root of 57 over denominator 76 end fraction end cell row cell sin space angle ABC end cell equals cell fraction numerator 3 square root of 57 over denominator 38 end fraction end cell row cell sin space angle ABC end cell equals cell arc space sin space open parentheses fraction numerator 3 square root of 57 over denominator 38 end fraction close parentheses end cell row cell sin space angle ABC end cell equals cell 36 comma 59 degree end cell end table

Maka, sin space angle ABC adalah 36 comma 59 degree.

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