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Logarithm

2:56

Logarithms - Basics | What are Logs? | Don't Memorise

3:34

Logarithms, Explained - Steve Kelly

3:27

Evaluating Basic Logarithms Without a Calculator

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Solving a simple logarithm

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Natural Logarithms

In mathematics, the logarithm is the inverse function to exponentiation. That means the logarithm of a given number x is the exponent to which another fixed number, the base b, must be raised, to produce that number x. In the simplest case the logarithm counts repeated multiplication of the same factor; e.g., since 1000 = 10 × 10 × 10 = 103, the "logarithm to base 10" of 1000 is 3. The logarithm of x to base b is denoted as logb (x) (or, without parentheses, as logb x, or even without explicit base as log x, when no confusion is possible). More generally, exponentiation allows any positive real number to be raised to any real power, always producing a positive result, so the logarithm for any two positive real numbers b and x where b is not equal to 1, is always a unique real number y. More explicitly, the defining relation between exponentiation and logarithm is: exactly if
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    • Other Scottish inventions  

    • Motivation and definition 

    • Particular bases 

    • History 

    • Logarithm tables, slide rules, and historical applications 

    • Analytic properties 

    • Calculation 

    • Applications 

    • Generalizations