# 6.7 $\vartheta”[x]$: Second-Order Derivative of First Chebyshev Function

The first plot below illustrates $\vartheta”[0]=0$ and $\vartheta”[x]$ is an odd function of $x$. The next three plots illustrate $\vartheta”[x]$ in the right=half plane at $f={1, 2, 3}$. The last plot below focuses around $x=19$ with evaluation frequencies $f={2, 4, 8}$.