As shown in the figure, circle $C_1$ with center $O_1$ and radius $r_1$ touches the square VWXY at points P and Q while circle $C_2$ with center $O_2$ and radius $r_2$ touches the square VWXY at points R and S. The two circles touch each other at T. Given r_1 = 1 cm and $\overline{VY}$ = $\overline{VW}$ = 4 cm, r_2 = _______ cm.