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 )
