Question

Please answer this question now

Answer 1

Answer:

$\boxed{u = 13.7}$

Step-by-step explanation:

Using cosine rule

$c^2 = a^2+b^2-2ab\ CosC$

Here c = u, a = 9 , b = 21 and C = 28

$u^2 = 9^2+21^2-2(9)(21)\ Cos 28\\u^2 = 81+441-(378)(0.88)\\u^2 = 522 - 333.75\\u^2 = 188.24$

Taking sqrt on both sides

u = 13.7

Answer 2

Answer:

u ≈ 13.7

Step-by-step explanation:

Using the Cosine rule in Δ STU, that is

u² = s² + t² - 2stcosU

Here s = 21, t = 9 and U = 28°, thus

u² = 21² + 9² - (2 × 21 × 9 × cos28°)

   = 441 + 81 - 378 cos28°

   = 522 - 378 cos28° ( take the square root of both sides )

u = $\sqrt{522-378cos28}$

   ≈ 13.7 ( to the nearest tenth )