Suppose that $C$ and $D$ are polyhedral convex sets in $R^n $and x is in $C \cap D$. show (a) $T_{C \cap D}(x)=T_C(x) \cap T_D(x)$
(b) $N_{C \cap D}(x)=N_C(x) + N_D(x)$
(c) compute the tangent and normal cone to $\{x|Ax=b, x>=0\}$.
Anyone know how to solve this problem?