Really sorry about that, the picture didn't get uploaded but it's there now, hope it gives you gives you better context and I did mean tau (didn't know it was spelt like that). dvcdt is just dV/dt as you said, but the voltage in the capacitor's voltage specifically not the source's.
The question that I'm having trouble with involves an RC circuit with a wire down the middle and two switches, I've attached a picture of it.
There are two parts to the question and it's the second part of it I'm having trouble understanding but I'll put in the first one for context anyway...