Which of the following is a property of the inner product ⟨u,v⟩\langle u, v \rangle⟨u,v⟩?
⟨u,v⟩=⟨v,u⟩\langle u, v \rangle = \langle v, u \rangle⟨u,v⟩=⟨v,u⟩ (for real vector spaces)
⟨u,u⟩<0\langle u, u \rangle < 0⟨u,u⟩<0 if u≠0u \neq 0u=0
⟨u,v+w⟩=⟨u,v⟩+⟨w,u⟩\langle u, v+w \rangle = \langle u, v \rangle + \langle w, u \rangle⟨u,v+w⟩=⟨u,v⟩+⟨w,u⟩
⟨u,v⟩\langle u, v \rangle⟨u,v⟩ must be an integer.