zuai-logo

Glossary

B

Base *e*

Criticality: 2

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, A=PertA = Pe^{rt}, uses base e to represent the exponential growth of money over time.

C

Change of Base Property

Criticality: 3

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 log4(64)\log_4(64) using a calculator that only has ln\ln or log\log, you can apply the Change of Base Property to get ln(64)ln(4)\frac{\ln(64)}{\ln(4)}.

D

Domain (of Logarithmic Functions)

Criticality: 2

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 f(x)=log(x+5)f(x) = \log(x+5), the domain requires that x+5>0x+5 > 0, meaning x>5x > -5.

G

Graphical Transformations (of Logarithmic Functions)

Criticality: 3

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 y=3log(x1)+2y = -3\log(x-1) + 2 demonstrates graphical transformations including a reflection, vertical stretch, horizontal shift right, and vertical shift up from the parent function y=log(x)y = \log(x).

I

Inverse (of Exponential Functions)

Criticality: 2

A function that 'undoes' the operation of another function; logarithmic functions serve as the inverse of exponential functions.

Example:

Since 102=10010^2 = 100, the inverse relationship means log10(100)=2\log_{10}(100) = 2, effectively reversing the exponential operation.

L

Logarithmic Functions

Criticality: 3

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 ln(2)\ln(2) will help you solve for time.

N

Natural Logarithm ($\ln(x)$)

Criticality: 3

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.

P

Power Property (of Logarithms)

Criticality: 3

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 log(1.03t)=log(5)\log(1.03^t) = \log(5), the Power Property allows you to bring 't' down as a multiplier: tlog(1.03)=log(5)t \log(1.03) = \log(5).

Product Property (of Logarithms)

Criticality: 3

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 log5(25x)\log_5(25x), you can use the Product Property to write it as log5(25)+log5(x)=2+log5(x)\log_5(25) + \log_5(x) = 2 + \log_5(x).

R

Range (of Logarithmic Functions)

Criticality: 1

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 y=logb(x)y = \log_b(x), the output can span from negative to positive infinity, illustrating its range is (,)(-\infty, \infty).