Quandaries and Queries Name: Jared Hello...I need to be able to calculate the radius of an arc on an existing structure (Supports for Fifth Ave Dimensional Text). I have the overall length of this structure, but, the complication I believe lies in the fact that it is a curve mounted onto a flat section of wall on either side of a very mild curve, therefore, measuring the middle of the wall to the top of the arc does me little good...The reason I need this is to be able to replicate the above curve  on a similar structure to be mounted below it...Also, because the client wants the structure mounted on the inside of the opening below the existing, the beginning and end point of the new structure would be lower than the existing, so, I do not believe that it is possible to exactly replicate the radius of the above curve? I have attached a photo...If you can tell me how to calculate this, it would be greatly appreciated. I have spoken to a fabrication shop who mentioned something about a rise/cord measurement? Hi Jared, My understanding is that you have two arcs on the same chord, you want the radius of the external arc but the "mild curve" of the interior arc doesn't allow you to measure the chord. My suggestion is that you select a point on the external arc and measure as long a chord as you can. Find the center of this chord and measure the height h of the exterior arc above the chord. Then use the method I applied to an earlier question to find the radius of the circle. Penny Go to Math Central