Respuesta :

mathnerd51
See the picture below

Answer:

x ≈ 11.89

Step-by-step explanation:

Using the cosine rule

x² = 4² + 9² - ( 2 × 4 × 9 × cos128° )

    = 16 + 81 - 72cos128°

     = 97 - (- 44.33 )

      = 141.33 ( take the square root of both sides )

x = [tex]\sqrt{141.33}[/tex] ≈ 11.89 ( to 2 dec. places )

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