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Glossary

C

Continuity

Criticality: 3

A property of a function where its graph can be drawn without lifting the pen, meaning it behaves smoothly without sudden jumps or gaps at a given point or interval.

Example:

A polynomial function like f(x)=x32x+1f(x) = x^3 - 2x + 1 is continuous for all real numbers, as its graph flows smoothly without any breaks.

D

Discontinuity

Criticality: 3

A point or interval where a function is not continuous, indicating a break, jump, or hole in its graph.

Example:

The function f(x)=1/(x1)f(x) = 1/(x-1) has a discontinuity at x=1x=1 because the function is undefined there, leading to a vertical asymptote.

Domain

Criticality: 1

The set of all possible input values (x-values) for which a function is defined and produces a real output.

Example:

The domain of the function f(x)=x4f(x) = \sqrt{x-4} is x4x \geq 4, because the expression under the square root must be non-negative.

F

Function value (f(c))

Criticality: 3

The specific output value of a function when a particular input 'c' from its domain is substituted into the function.

Example:

For the function f(x)=x2+5f(x) = x^2 + 5, the function value at x=2x=2 is f(2)=22+5=9f(2) = 2^2 + 5 = 9.

J

Jump discontinuity

Criticality: 2

A type of discontinuity where the left-hand limit and the right-hand limit at a point both exist but are not equal, causing a sudden 'jump' in the graph.

Example:

The greatest integer function, f(x)=xfloorf(x) = \lfloor x floor, has a jump discontinuity at every integer value, as the function value abruptly changes.

L

Left-hand limit

Criticality: 2

The value a function approaches as the input (x) gets arbitrarily close to a specific point 'c' from values less than 'c'.

Example:

For a piecewise function f(x)=x+1f(x) = x+1 for x<2x<2, the left-hand limit as x approaches 2 is 2+1=32+1=3.

Limit of a function

Criticality: 3

The value that a function approaches as its input (x) gets arbitrarily close to a specific point 'c', regardless of the function's actual value at 'c'.

Example:

For f(x)=(x29)/(x3)f(x) = (x^2-9)/(x-3), the limit of the function as x approaches 3 is 6, even though the function is undefined at x=3x=3.

R

Removable discontinuity

Criticality: 2

A type of discontinuity where the limit of the function exists at a point, but the function value is either undefined or does not match the limit, often appearing as a 'hole' in the graph.

Example:

The function f(x)=(x21)/(x1)f(x) = (x^2-1)/(x-1) has a removable discontinuity at x=1x=1 because it can be simplified to x+1x+1 for xeq1x eq 1, creating a hole at (1,2)(1,2).

Right-hand limit

Criticality: 2

The value a function approaches as the input (x) gets arbitrarily close to a specific point 'c' from values greater than 'c'.

Example:

For a piecewise function f(x)=2x1f(x) = 2x-1 for x2x \geq 2, the right-hand limit as x approaches 2 is 2(2)1=32(2)-1=3.

V

Vertical asymptote

Criticality: 2

A vertical line $x=c$ that the graph of a function approaches but never touches, typically occurring where the function's denominator is zero and the numerator is non-zero.

Example:

The function f(x)=an(x)f(x) = an(x) has vertical asymptotes at x=π/2+nπx = \pi/2 + n\pi (where n is an integer), as the function's value approaches infinity or negative infinity at these points.