1. The problem statement, all variables and given/known data Prove the Int<ABC is a convex set. 2. Relevant equations 3. The attempt at a solution 1. Int <ABC = H(A,BC) intersect H(C,AB) by the definition of interior. 2. H(A,BC) is convex and H(C,AB) is convex by Half-Plane Axioms I know I need to show the intersection of the two half planes is convex but I do not know how to do this.