Transfer of Ideas Math Example 4

Follow the full solution, then compare it with the other examples linked below.

Example 4

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The proof technique 'assume the hypothesis and derive the conclusion' (direct proof) from logic transfers to proving: 'If ff and gg are continuous at aa, then f+gf+g is continuous at aa.' Sketch the transferred argument structure.

Solution

  1. 1
    Assume the hypothesis: ff is continuous at aa (i.e., limxaf(x)=f(a)\lim_{x\to a}f(x)=f(a)) and gg is continuous at aa.
  2. 2
    Derive: limxa(f+g)(x)=limxaf(x)+limxag(x)=f(a)+g(a)=(f+g)(a)\lim_{x\to a}(f+g)(x) = \lim_{x\to a}f(x)+\lim_{x\to a}g(x) = f(a)+g(a) = (f+g)(a).
  3. 3
    Conclusion: f+gf+g is continuous at aa.

Answer

f+g is continuous at af+g \text{ is continuous at } a
The direct-proof structure (assume hypothesis, derive conclusion) from propositional logic transfers directly to analysis proofs. The same logical skeleton works regardless of the mathematical content.

About Transfer of Ideas

The ability to recognize that a technique or concept from one area of mathematics applies, possibly in adapted form, to a different area.

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