[[Calculus 3]]
- Level curve
	- A 2D shape that results from setting a two-variable equation equal to a constant
	- can help to see the shape of a 3D function
	- basically like taking horizontal slices out of a two-variable function
- Vertical trace
	- similar to level curve, finding the 2D shape from a vertical slice
	- can find with either $f(a, y) = z$ for constant $x = a$ or $f(x, b) = z$ for constant $y=b$
- Both of these are used to visualize 3D functions in 2D
- Functions of 3 variables
	- there is no great way to visualize these in 3 dimensions
	- have to take 3D "slices" out of the 4D shape