Sketch the level curves for the function $\displaystyle z = ln(x^2 + y^2)$.

Attempt:

$\displaystyle k = ln(x^2 + y^2)$

$\displaystyle z = ln(k^2 + y^2)$

$\displaystyle z = ln(x^2 + k^2)$

Now I am not sure how I would draw each of these graphs due to the $\displaystyle ln(x^2 + y^2)$ part.

Also when asked to sketch the level curves, does that mean you just let z = k and draw one graph? (as opposed to also letting x = k and y = k)