# Torsional Constant of Thin-Walled Multi-Cell Structures

I'm asked to analytically calculate the composite torsional constant of the following structure.

No other information is given, such as the applied torque.

I know how to calculate the torsional constant for each component (an equilateral triangle and a semicircle), but I don't think I can just add them weighted to the areas.

Is there anything else I can try?