I am working through a modulo tutorial and have become stuck here: $ 11^{32}(\operatorname{mod}13) = (11^{16})^2(\operatorname{mod}13)= 3^2(\operatorname{mod}13)= 9(\operatorname{mod}13) $
My question is, how does $(11^{16})^2(\operatorname{mod}13)$ get reduced to $3^2(\operatorname{mod}13)$?