Using Law of cosines, you'll find the smallest angle is between the 34 and 47 sides and = 29.23 =29 to the nearest degree.
24^2 = 34^2 + 47^2 - 2(34)(47)COS(angle)
See: http://mathworld.wolfram.com/LawofCosines.html for a good description of Law of Cosines