Question:
Let $[t]$ denote the greatest integer $\leq t$. The number of points where the function
$$
f(x)=[x]\left|x^{2}-1\right|+\sin \left(\frac{\pi}{[x]+3}\right)-[x+1], x \in(-2,2)
$$ is not continuous is
Solution:
$f(x)=[x]\left|x^{2}-1\right|+\sin \frac{\pi}{[x+3]}-[x+1]$
$f(x)=\left\{\begin{array}{cc}3-2 x^{2}, & -2 discontinuous at $x=0,1$