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Part CCSIR NET June 2024immersion-is-not-submersion

Immersion is not submersion

Let be a differentiable function such that (Df)(0,0) has rank 2. Write . Which of the following statements are necessarily true?

  1. A.f is injective in a neighbourhood of (0, 0)
  2. B.There exists an open neighbourhood U of (0, 0) in such that is a function of and
  3. C.f maps an open neighbourhood of (0, 0) in onto an open subset of
  4. D.(0, 0) is an isolated point of f⁻{f(0,0)})

You have the answer. Trap Analysis is why the other three were written.

Not a worked solution repeated four times — the specific reasoning error each wrong option was built to reward.

See pricing

50 are analysed free — try those first.

Related counterexample: A C¹ map with everywhere non-zero Jacobian is injective

More on this topic

The chapter behind this: Inverse and implicit function theorems — free to read

From Functions of Several VariablesInverse and implicit function theorems, extrema

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