Answer
$0$
Work Step by Step
We will use the following limit rules for this problem:
$ \ Rule -\ 1 \ : \lim\limits_{x \to a} [A(x)]^n =[\lim\limits_{x \to a} A(x)]^n $
$\ Rule \ - \ 2 : \lim\limits_{x \to a} A(x)=A(a)$
Apply the given rules:
$\lim\limits_{x\to 1}(\sqrt {1-x^2})=[\lim\limits_{x\to 1}\sqrt {1-x^2}]\\=\sqrt {1-1^2} \\=\sqrt {0}\\=0$
