Mathematics I / Introduction to Differential Equations
Practice question · Multiple choice

The "split into thin pieces" argument gives the right arc length with dsds but the wrong surface area if you use dxdx instead. What fails?

Hints
  1. Approximate a diagonal line by horizontal steps and measure the staircase.
  2. What does the staircase converge to in shape, and in length?
Show the answer

B. The piece is no longer nearly simple where it matters

Why

The staircase paradox: the shape converges and the length does not. Additivity is not enough, the piece must be nearly simple in the quantity being measured, which is why dsds and not dxdx appears.

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