The surface area of a cell in a honeycomb is

wherehandsare positive constants and θ is the angle at which the upper faces meet the altitude of the cell. Find the angle θ (π/6 ≤ θ ≤ π/2) that minimizes the surface areaS.

I started by taking the first derivative of S, but I was still left with multiple variables, even though h and s are constants. I'm not sure how to actually do this problem. Any help?

Thanks