This problem can be solved in 8 steps:
1. Let AB = C
2. A-1AB = A-1C
3. IB = A-1C as the identity matrix I = A-1A
First we set y=artanh(x). Then we rearrange such that tanh(y)=x. There several approaches to find dy/dx, but the quickest is to use implicit differentiation.
The differential of tanh(y) is sech