Solution (source code)

= Solution

The <function composition> of two <bijections> is a <bijection>. Its <inverse function> is two-sided, so
$$
\boxed{\text{True: }(f\circ g)\circ(f\circ g)^{-1}=\operatorname{id}.}
$$
This is exactly the defining cancellation property of an <inverse function>, with the whole <function composition> regarded as one <function>.