Determine the unit normal vector to the surface x+y+z=1x + y + z = 1x+y+z=1 at (0,0,1)(0, 0, 1)(0,0,1).
⟨1,1,1⟩/3\langle 1, 1, 1 \rangle / \sqrt{3}⟨1,1,1⟩/3
⟨1,0,0⟩\langle 1, 0, 0 \rangle⟨1,0,0⟩
⟨0,0,1⟩\langle 0, 0, 1 \rangle⟨0,0,1⟩
⟨1,1,0⟩/2\langle 1, 1, 0 \rangle / \sqrt{2}⟨1,1,0⟩/2