$$\sqrt{1 - (-1 + x\bmod 2)^2}\cdot\operatorname{sign}(-2 + x\bmod 4)$$
Like half-circles connected to each other to look like waves:
plot http://vi-server.org/vi/_/func.png
Its plot looks smooth, but the function is actually not smooth.
$$\sqrt{1 - (-1 + x\bmod 2)^2}\cdot\operatorname{sign}(-2 + x\bmod 4)$$
Like half-circles connected to each other to look like waves:
plot http://vi-server.org/vi/_/func.png
Its plot looks smooth, but the function is actually not smooth.