Question

Please explain how to do and set up

Answer 1

A

using the Cosine rule in ΔSTU

let t = SU, s = TU and u = ST, then

t² = u² + s² - (2us cos T )

substitute the appropriate values into the formula

t² = 5² + 9² - (2 × 5 × 9 × cos68° )

   = 25 + 81 - 90cos68°

   = 106 - 33.71 = 72.29

⇒ t = $\sqrt{72.29}$ ≈ 8.5 in → A