(a) Let C be a nonempty convex cone. Show that cl(C) and ri(C) is also a convex cone. 

(b) Let C = cone({x1, . . . , xm}). Show that

2. Let C1 and C2 be convex sets. Show that

m ri(C) = {a;a;|a; > 0, i = 1,...,m}. %3D i=1