Glossary
Base *e*
An irrational mathematical constant approximately equal to 2.71828, which is the base of the natural logarithm and is fundamental in continuous growth and decay processes.
Example:
The formula for continuous compound interest, , uses base e to represent the exponential growth of money over time.
Change of Base Property
Allows you to convert a logarithm from one base to another, typically to use a calculator's common (base 10) or natural (base e) logarithm functions.
Example:
To calculate using a calculator that only has or , you can apply the Change of Base Property to get .
Domain (of Logarithmic Functions)
The set of all valid input values (x-values) for which a logarithmic function is defined, which must always be positive real numbers.
Example:
For the function , the domain requires that , meaning .
Graphical Transformations (of Logarithmic Functions)
Changes to the position, size, or orientation of a logarithmic function's graph, such as shifts, stretches, compressions, or reflections, caused by altering its algebraic form.
Example:
The graph of demonstrates graphical transformations including a reflection, vertical stretch, horizontal shift right, and vertical shift up from the parent function .
Inverse (of Exponential Functions)
A function that 'undoes' the operation of another function; logarithmic functions serve as the inverse of exponential functions.
Example:
Since , the inverse relationship means , effectively reversing the exponential operation.
Logarithmic Functions
Functions that are the inverse of exponential functions, used to determine the exponent to which a base must be raised to produce a given number.
Example:
If you're trying to find out how many years it takes for an investment to double with continuous compounding, a logarithmic function like will help you solve for time.
Natural Logarithm ($\ln(x)$)
A specific type of logarithm with base *e* (Euler's number), denoted as $\ln(x)$, which is the inverse function of $e^x$.
Example:
In modeling continuous growth, such as bacterial population, you might use the natural logarithm to find the time it takes to reach a certain population size.
Power Property (of Logarithms)
States that the logarithm of a number raised to a power is equal to the product of the power and the logarithm of the number.
Example:
When solving for 't' in an equation like , the Power Property allows you to bring 't' down as a multiplier: .
Product Property (of Logarithms)
States that the logarithm of a product of two numbers is equal to the sum of their individual logarithms with the same base.
Example:
To expand , you can use the Product Property to write it as .
Range (of Logarithmic Functions)
The set of all possible output values (y-values) for a logarithmic function, which for basic logarithmic functions is always all real numbers.
Example:
No matter how large or small the positive input to , the output can span from negative to positive infinity, illustrating its range is .