place a v5 point on the inflection point of a curve?

The Point of Inflection on a curve can be found using the Porcupine Analysis tool that is in GSD. I am using Release 9 for this, it won't be much different on other releases. The images have been borrowed from the Help Documentation and are for a guide only.

From the bar at top of screen select Insert => Analysis => Porcupine Analysis



In the box, use Curvature, select Diagram and pick Particular and Envelop. The Comb is not needed. In the model, the Envelop curve will be seen to cross the object curve and at that point inflection occurs. If the object curve has no inflection then the Envelop curve will never touch it.



The curve in the Diagram box represents curvature, so where it touches the lower (Y=0) axis is a point, the curvature is zero as the radius of curvature here is infinite.
Left click this point and it says 'Use this Point'. Now Right click it and up comes several options. Select 'Drop X' and an explicit point is added to the Specification Tree.
This is the Point of Inflection on the curve being analised.

you need GSD + GSO in order to have the Graph...

Thanks, kapitan, but itsmyjob is right.