# Let's draw

Calculus Level 4

Given that,

$\large f(x) = \color{blue}{\text{max}} \begin{cases} \text{sgn}(x) \\ x^3 \\ -\sqrt{9 - x^2} \hspace{.3cm} \small\text{ where defined} \\ -x^2 \end{cases}$

The number of points where the function $$f(x)$$ is not differentiable for $$x\in\Bbb R$$ are ....?

Bonus:

• Draw the graph for quick solution.
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