Every $A \in \text{GL}_n(\mathbb{R})$ has a unique [Polar decomposition][1]: $A=O_AP_A$, $O \in \operatorname{O}_n, P \in \operatorname{Psym}_n$. In particular the orthogonal factor is given by $$O_A=A(\sqrt{A^TA})^{-1}.$$ **Question:** Let $A,B \in \operatorname{GL}_n^+$. Does there exist a positive constant $c<1$ such that $$ |AB-O_{AB}| \ge c|AB-O_AO_B|$$ **Motivation:** $O_A$ is the [closest matrix in $\text{SO}_n$ to $A$][2]; We can think of it as the isometric projection of $A$. This projection is not multiplicative ($O_{AB} \neq O_AO_B $ for some $A,B$). My question concerns the boundedness of the "error" (in computing the distacne from $\text{SO}_n$) when using $O_A O_B$ instead of $O_{AB}$. [1]:https://en.wikipedia.org/wiki/Polar_decomposition [2]:http://math.stackexchange.com/questions/1477855/distance-of-a-matrix-from-the-orthogonal-group [3]:http://math.stackexchange.com/a/1910835/104576