Real Elementary Functions are Continuous

Theorem

The elementary functions on the real numbers $\R$ are all continuous at every point of their domain.


Proof

In turn:

Real Polynomial Function is Continuous
Real Trigonometric Functions are Continuous
Real Logarithm Function is Continuous
Real Exponential Function is Continuous

It remains to show that:

All real functions that are compositions of the above
All real functions obtained by adding, subtracting, multiplying and dividing any of the above types any finite number of times

are also continuous at every point of their domain.


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Sources

  • 1998: David Nelson: The Penguin Dictionary of Mathematics (2nd ed.) ... (previous) ... (next): continuous function (continuous mapping)
  • 2008: David Nelson: The Penguin Dictionary of Mathematics (4th ed.) ... (previous) ... (next): continuous function (continuous mapping, continuous map)