Making a reverse part of a circle

I am trying to rez a "wave" pattern for decoration which includes a circle and a reverse circle together. Does anyone know how I could accomplish this (the reverse circle)? I have twisted and turned and hollowed away, but can't seem to make this essential shape? I attached a crude example drawing to illustrate the goal.

Looks like a prim heavy shape to me with a mixture of cut circles and cut, rotated and circle hollowed boxes. I doubt you can do this in one prim. It'll be basically 2 prims per wave.

Use a box prim, rotate so that the Z axis is paralell to the floor, hollow to 95 with circle hollow style, and cut until you get about "Cut begin and end: 0.35 0.90". Rotate once more around the Y axis this time so the hole is the right side up Et voila. Now you can continue with half-cylinders for the wave part, and filling with box prims. You will probably have to adjust the cut amount manually to get a clean junction of the prims.

I dropped an object like that on you in-world so if the explanation is unclear, just rez it and have a look.

Ah yes! That is it. Sometimes it is good to get outside suggestions to "think outside the box." Thank you