Maybe this is my inexperience, but this seems inconsistant and just plain weird.
Is there a way to create tangency with a spline between other sketch entities? Here's the situation. I want to create a 3 point spline with a spiral attached tangent to each endpoint. So, I opened a sketch, draw a 3 pt spline with the center coincident to the origin then continue to fully define the sketch. Exit the sketch, start a new one... since that is how you have to draw a helix/spiral... I put in a simple circle and it wont allow me to apply tangency to the spline. I called the VAR and their solution was to open the original sketch and offset the spline at a distance of the radius of the circle of the other sketch, then make the circle center coincident to the offset spline. This works. OK great. But heres the weirdness. I found that I can make lines, arcs, circles, and new splines tangent to the offset spline... WHAT?? but not the original? Is this a bug? Can anyone explain this, or at least justify the peculiar behavior? I have included an example for reference (SW2011 sp03). As a watch out warning with splines, tangency, in this case, seems to be anchored to where you click, and not the entire curve.