Is there an approximation function for this function?

Question

The function is: $$f(x,y)=\frac{x}{\log\left(1+\frac{1}{1+y}\right)}$$ where $x\in [0,1], y \in [0,1] $,and the approximation function can split $x$ and $y$.

The result is like this:$f(x,y) = f_1(x)+f_2(y)$.