Lenght of arc in 2d mode

[anoc]

How do I get the lenght-dimension of arc in inventor 6 drawing(Sheet, not in 3D sketch) -mode from some object including arc / circle / half circle?
What tool and how should I click to get it?

 

[autocol]

normal dimension tool.

click arc, then before you place the dimension right click and choose "arc length" from the "dimension type" list...

 

[anoc]

Thanks!
I don't understand why the dimension doesn't always show, after pressin the "lenght arc" option. It worked in a new part, but not in old, maybe it's coz of the old part was created with Inv5

Problem solved, thanks!