If the point you’re looking for is always going to be the cross section of the two components, you only need to look at the position (location) of the components. In the case of your screenshot (with X going in the up/down direction), the (X,Y) location of V3 would be at (V1, V2). That is, you can use the X of V1 and the Y of V2 to determine where V3 will be. As for the height of V3 (Z), this would depending on what exactly you’re trying to do, but you could simply get the actor’s Z and use that if you wanted V3 to be at the same height as the actor.
Assuming the actor is rotating in place, this setup will move V3 back and forth on an X/Y diagonal. If you want V3 to stay in the same place relative to V1 and V2 such that V3 is revolving around the actor’s origin, then further math calculations would be necessary to determine that.