$$\left.\begin{array}{rr} (U\in\sigma)(f, \,\ (\tau\mbox{-}\sigma) \text{ sürekli})\Rightarrow f^{-1}[U]\in\tau \\ \\ (f_A)^{-1}[U]=A\cap f^{-1}[U] \end{array}\right\}\Rightarrow (f_A)^{-1}[U]\in\tau_A.$$
Teşekkür ederim hocam.