Sketcher weirdness

[pausob]

Have you have come across a situation where the sketcher is acting strangely?

In this case, after trimming off a bunch of lines, the sketcher unexpectedly added in dimensions.  When I investigated this by using the "Modify Dimensions" tool to change the value of the dimension shown, the highlighted (vertical) line moves left to right.  And yet the sketcher keeps insisting that this line is tangent to the fixed-size arc at the bottom:

[VladimirN]

Please specify which version of the program you are using.

[pausob]

I've recreated the "issue" on a new part.  Creo 4 M150

Model sketch_test.prt, feature #15 - "Sketch 5"

Selecting the “T”angent constraint, and performing the “explain” command:

I attach the model and a few slides to show how it was made.

I suppose I'm wondering if there's something I am missing in my basic understanding about tangency / geometry.

[kdirth]

That is weird.  It seems the tangencies are between the end points of the arcs and the lines (all 4 of them).  If you drag the endpoint of the arc the line moves.  It appears that the line remains parallel with the end of the arc.

If I add my own tangency between the arc and the line (Creo 7) it snaps to where I expect it and the "point tangency" remains with no conflict.

[pausob]

Hmm, I don't think I understand your terminology - how a line can be tangent to an end-point of an arc, or remain parallel to an end of an arc?

I suppose it can in Creo 😁  Anyway, so this weirdness is still there in newer versions.  Anyone from PTC care to comment?

[kdirth]

I wasn't able to recreate the odd tangency that you have in your model but 7.0 did not reject it either.  I don't know the process you used to create it 

Basically, it appears to be creating a parallel to an imaginary line tangent to the end of the arc.