Answer:
R =70.6970629
Explanation:
We need to use the law of cosines since we have 2 sides and the included angle
The angle inside is 180 -50 = 130
c^2 = a^2 + b^2 − 2ab cos(C) where c is the side opposite the unknown angle
R^2 = 40^2 + 38^2 - 2*40 *38 cos (130)
R^2 = 1600 -1444-3040cos 130
R^2 = 3044-3040cos130
R^2 =4998.074333
Taking the square root of each side
sqrt(R^2) = sqrt( 4998.074333)
R =70.6970629