Solution
= Solution
The radial coordinate in the <cylindrical coordinate system> is the <Euclidean distance> from the $z$-axis:
$$
\boxed{r=\sqrt{x^2+y^2}=\sqrt2}.
$$
= Solution
The radial coordinate in the <cylindrical coordinate system> is the <Euclidean distance> from the $z$-axis:
$$
\boxed{r=\sqrt{x^2+y^2}=\sqrt2}.
$$