This is just a follow up question to an solution you already provided me. Could you please explain in detail the moment taken around C?

This is just a follow up question to an solution you already provided me. Could you please explain in detail the moment taken around C? [specifically..how you you came up with (Fgjsin30*10) +(Fgjcos30)(5.77)] I understand how you calculated JD (5.77), just which 30 degree angle did you use specifically etc...Thanks.