Question

Given that x = 5.7 m and θ = 43°, work out BC rounded to 3 SF​

Answer 1

Use SOH CAH TOA
label sides hypotenuse, adjacent
cos43 = adjacent / hypotenuse

BC/AC = BC/5.7

x both sides by 5.7

5.7 x cos43 =BC

BC = 4.17(3sf)

Answer 2

BC ≈ 4.17

Explanation:

Using the cosine ratio in the right triangle

cos43° =
`(adjacent)/(hypotenuse)` =
`(BC)/(AC)` =
`(BC)/(5.7)` ( multiply both sides by 5.7 )

5.7 × cos43° = BC , then

BC ≈ 4.17 ( to 3 sf )