How to draw/measure arc

Hi i am new to the world of 3d modelling and engineering. Although i am ok with the actual use of Inventor, i am struggling with the reverse engineering side.

I have a part which i am trying to replicate in Inventor (see attached) the part has 2 curves on it's sides.

What is the easiest way to determine the arc measurements so i can design this.

I would appreciate an help offered.

thanks

Andy

i would measure from each outer point and the depth from the surface to the lowest point of the arc. so then points can be placed at these points and joined with a 3 point arc.

bit like that. as you can see there are 3 points where u can get the dimension from the workpiece. then using the arc tool just click the two points on the flat and then the third one con straining the depth....

hope that makes sense :/

Building on Roberts solution - it might be easier to measure across the arcs rather than from flat to arc depth. Become familiar with geometry constraints and using construction lines. I made the 4 vertical lines all = constraint (if the are equal) reducing the number of dimensions.

You might also read this http://home.pct.edu/~jmather/skillsusa%20university.pdf

Thank you so much for your very helpful responses....i must sound like a right donut! thanks again

no problem, both ways are simple. only difference is i used derived dimensions where as jd made his lengths equally constrained. hope this gives you the outcome needed!

cheers Rob