The Implicit Function Theorem
An interactive live film: the surface F(x, theta) = x^2 + theta^2 - 4 meets height zero in a circle; drag a point along it to see the slope dx*/dtheta = -(dF/dx)^(-1) dF/dtheta from two slices, and find where dF/dx = 0 and the theorem fails.
Narration
Here is a surface, F of x and theta equals x squared plus theta squared minus four, over the floor of theta and x. The light sheet marks height zero.
Where the surface crosses the sheet, F equals zero: the green circle, copied onto the floor, holds every pair where x star of theta solves the equation.
The rest of the narration is in the book's Companion.
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