Answer:
15.43 km^2
Explanation:
If base of triangle is 8 km, then height will be the line from vertex which is perpendicular with base
sin(40) = height/6
0.64278761 = height/6
height = 0.64278761 x 6 = 3.85672566
then area = 1/2 (3.85672566 x 8) = 15.42690264 or 15.43