Chapter 2 - Differentiation - 2.1 Exercises - Page 105: 86

Because the function is not continuous at x=1, it is not differentiable at x=1.

$\lim\limits_{x \to 1^-}\sqrt {1-x^2}=0$ $\lim\limits_{x \to 1^+}\sqrt {1-x^2}$ is undefined Because the function is not continuous at x=1, it is not differentiable at x=1.