Answer:
BC ≈ 14.7 m
Step-by-step explanation:
Using the Sine rule in Δ ABC
[tex]\frac{AB}{sinC}[/tex] = [tex]\frac{BC}{sinA}[/tex]
To find ∠ A subtract the 2 given angles from 180°
∠ A = 180° - (90 + 28)° = 180° - 118° = 62°
Then
[tex]\frac{7.8}{sin28}[/tex] = [tex]\frac{BC}{sin62}[/tex] ( cross- multiply )
BC × sin28° = 7.8 × sin62° ( divide both sides by sin28° )
BC = [tex]\frac{7.8sin62}{sin28}[/tex] ≈ 14.7 m ( to 3 significant figures )
