Two intersacting lines won't create a new shape why?

Question

I've a little problem extruding a form of two intersecting lines. First I created a sketch, then I projected the relevant points onto and finally I drew my circle. But now I can't select the intersecting form which I want to extrude (marked as red).

It either selects the projected form or the circle.

Does anyone have an idea? I haven't figured out much so far.

Answer 1

they are probably not on the same sketch. try projecting the lines into the new sketch using the project tool. make sure 3d sketch is turned off, it breaks things and should only be used when absolutely needed.