What does the “unused” output on the Vector Math node do?

The Vector Math node has two output sockets, Vector (vector type) and Value (scalar type).

Most of the vector operations (Normalize, Cross Product, Average, Subtract, and Add) result in vectors, what does the Value socket output when one of these operations is selected? Likewise, what does the Vector socket output when Dot Product (which results in a scalar) is selected?

• Surely you have your answer here with this one ? blender.stackexchange.com/questions/62309/… – lemon Sep 4 '16 at 8:23
• @lemon Ummmm... no... There I am asking if a specific function of the VM node uses both inputs, here I am asking what the outputs give when any function is selected. – PGmath Sep 4 '16 at 13:35

For add and subtract the Value output is the average of the absolute vector values. That is: $$\text{value} = \frac{\left\vert v_x\right\vert + \left\vert v_y\right\vert + \left\vert v_z\right\vert}{3}$$