Function of two variables - level curve
Instructions:
1. Key in the function you would like to visualize into the input box.
2. You can click and drag on the 3D curve to zoom in and out, or rotate the curve to see it from all sides.
3. Use the checkbox to see a horizontal intersecting plane.
4. Use the slider to change the value of z, which moves the intersecting plane up and down.
5. Refresh the page if anything