# What is the derivative of x=1?

The derivative with respect to $x$ requires a function of $x$ in its definition.
$x = 1$ does not describe a function of $x$. So it is not possible to give a definition of the derivative with respect to $x$. (It does not exist.)
If we think of it as a function of some other variable $t$, we can say $\frac{d}{\mathrm{dt}} \left(x\right) = \frac{d}{\mathrm{dt}} \left(1\right) = \frac{d}{\mathrm{dt}} \left(0 t + 1\right) = 0$