S = 1/2 * 20 * 8 rad(3) sin B^
sin B^ = sin (2/3 pi - C^) =
= sin 2/3 pi cos C^ - cos 2/3 pi sin C^ =
= rad(3)/2 * 4/5 + 1/2 * 3/5 =
= [4 rad(3) + 3]/10
S = 80 rad(3)/10 * (4 rad(3) + 3) =
= 8 (12 + 3 rad(3)) =
= 8*3 (4 + rad(3)) =
= 24 ( rad(3) + 4)