Answer:
? ≈ 12.34
Explanation:
using the Cosine rule in the triangle
a² = b² + c² - 2bc cosA
where b and c are known and A is the angle between them
here b = 12 , c = 7 , ∠ A = 76° , then
?² = 12² + 7² - ( 2 × 12 × 7 × cos76° )
= 144 + 49 - ( 168 × cos76°)
= 193 - 40.643
= 152.357 ( take square root of both sides )
? =
≈ 12.34 ( to the nearest hundredth )