↔️ Interval Notation Calculator

Convert Inequalities to Interval Notation

The Interval Notation Calculator is a handy tool for algebra students to practice converting between inequality expressions and interval notation. Interval notation is a concise way to describe a set of real numbers between two endpoints. This calculator helps you get comfortable with the syntax and rules for writing intervals.

Interval Notation Calculator

Convert between interval notation, inequality notation, and set-builder notation. Perform operations on intervals including union, intersection, and complement. Visualize intervals on a number line.

Calculator Mode

Input Interval

Format: Use ( or [ for left bracket, ) or ] for right bracket. Use ∞ or inf for infinity. Examples: (1, 5), [-2, 3], (-∞, 0), [0, ∞)

Display Options

About Interval Notation

Interval notation is a mathematical notation used to represent a subset of real numbers between two endpoints. It provides a concise way to describe continuous ranges of values and is widely used in calculus, analysis, and algebra.

Interval Notation Symbols
  • ( or ) - Open bracket: endpoint is NOT included (strict inequality)
  • [ or ] - Closed bracket: endpoint IS included (non-strict inequality)
  • ∞ or -∞ - Infinity: extends without bound (always uses open brackets)
Types of Intervals
  • Open Interval: (a, b) means a < x < b (neither endpoint included)
  • Closed Interval: [a, b] means a ≤ x ≤ b (both endpoints included)
  • Half-Open Interval: [a, b) or (a, b] (one endpoint included)
  • Unbounded Interval: (a, ∞), (-∞, b], (-∞, ∞) (extends to infinity)
  • Singleton: [a, a] contains only one point
  • Empty Set: ∅ or (a, a) contains no points
Interval Operations
  • Union (A ∪ B): All elements in A or B or both
  • Intersection (A ∩ B): Elements common to both A and B
  • Complement (A'): All real numbers NOT in A
  • Difference (A - B): Elements in A but not in B
Converting Between Notations

Interval to Inequality:

  • (a, b) → a < x < b
  • [a, b] → a ≤ x ≤ b
  • (a, ∞) → x > a
  • (-∞, b] → x ≤ b

Inequality to Interval:

  • x > 5 → (5, ∞)
  • -3 ≤ x < 7 → [-3, 7)
  • x ≠ 2 → (-∞, 2) ∪ (2, ∞)
Common Applications
  • Domain and range of functions
  • Solution sets for inequalities
  • Continuity and differentiability intervals
  • Confidence intervals in statistics
  • Constraints in optimization problems
Important Properties
  • Infinity (∞) is never included in an interval (always use open bracket)
  • An interval [a, b] is valid only if a ≤ b
  • The empty set ∅ can be represented as (a, a) where a is any real number
  • The set of all real numbers ℝ is represented as (-∞, ∞)

Understanding Interval Notation and the Calculator’s Purpose

The Interval Notation Calculator helps users convert, interpret, and analyze mathematical intervals. An interval represents a range of real numbers between two endpoints, showing whether each endpoint is included or excluded. This calculator simplifies how these ranges are expressed and visualized across multiple notations used in mathematics.

Common Interval Notation Examples:

  • (a, b) → a < x < b (both endpoints excluded)
  • [a, b] → a ≤ x ≤ b (both endpoints included)
  • (a, ∞) → x > a (extends to infinity)
  • (-∞, b] → x ≤ b (extends to negative infinity)

What the Calculator Does

This calculator provides three main modes to help students, teachers, and professionals handle interval-related problems efficiently:

  • Convert Notation: Instantly convert between interval, inequality, and set-builder notation.
  • Perform Interval Operations: Calculate the union, intersection, difference, or complement of intervals.
  • Solve Inequalities: Find the solution set of linear inequalities and express them in interval form.

The calculator also provides a visual representation on a number line, showing open or closed endpoints, infinite ranges, and overlaps between intervals. This makes abstract mathematical concepts easy to understand visually.

How to Use the Calculator

Using the Interval Notation Calculator is simple. Follow these steps:

  • Select a mode — Convert Notation, Interval Operations, or Solve Inequality.
  • Enter your input:
    • In Convert Mode, type an interval like (2, 5] or an inequality such as 2 < x ≤ 5.
    • In Operations Mode, input intervals A and B, and choose an operation such as Union (A ∪ B).
    • In Solver Mode, type an inequality (e.g., 2x + 3 ≥ 7).
  • Click Calculate to view the result, explanation, and number line visualization.
  • Use Reset to clear all fields and start again.

Formulas and Key Concepts

Here are the basic mathematical relationships the calculator uses to describe intervals and inequalities:

  • Interval to Inequality: (a, b) → a < x < b
  • Inequality to Interval: x ≥ a → [a, ∞)
  • Union (A ∪ B): All values in A or B
  • Intersection (A ∩ B): Values common to both A and B
  • Complement (A′): Values not in A

These formulas are essential for understanding relationships between sets of numbers in algebra and calculus. The calculator automates these transformations, ensuring accuracy and consistency.

Benefits and Practical Uses

The Interval Notation Calculator can be a valuable learning and productivity tool for:

  • Students: Check homework or visualize solutions to inequalities.
  • Teachers: Demonstrate interval relationships and operations in class.
  • Mathematicians and Data Analysts: Define numerical domains, constraints, or ranges efficiently.
  • Statisticians: Interpret confidence intervals and continuous ranges.

By showing results in multiple formats and visualizing intervals, users can gain a clear and intuitive understanding of mathematical relationships without manual calculation errors.

Frequently Asked Questions (FAQ)

What is interval notation?

Interval notation expresses all real numbers between two endpoints. It tells whether the endpoints are included (closed) or excluded (open).

Can I use infinity (∞) in my intervals?

Yes. You can use ∞ or -∞ to represent unbounded intervals. These always use parentheses, since infinity is never included.

What does an empty interval mean?

An empty interval, written as ∅ or (a, a), means there are no numbers that satisfy the given condition.

What do the symbols mean?

  • ( or ): Endpoint excluded (open interval)
  • [ or ]: Endpoint included (closed interval)
  • ∪: Union — combine intervals
  • ∩: Intersection — overlap between intervals

Can I visualize my interval?

Yes. The calculator draws a number line showing open and closed endpoints, shaded ranges, and arrows for infinite intervals, helping you see the solution range clearly.

Conclusion

The Interval Notation Calculator is a practical and user-friendly tool that simplifies how mathematical intervals are understood and presented. Whether you are converting between notations, solving inequalities, or performing interval operations, this calculator provides accurate results, clear explanations, and visual insights to make learning and analysis easier.

More Information

Rules for Interval Notation:

  • Parentheses ( ): Used when an endpoint is not included in the interval. This corresponds to the symbols < and >.
  • Brackets [ ]: Used when an endpoint is included in the interval. This corresponds to the symbols ≤ and ≥.
  • Infinity (∞): Infinity is not a number, so it always uses a parenthesis.
  • Union Symbol (∪): Used to combine two or more separate intervals.

For example, the inequality -2 ≤ x < 5 is written in interval notation as [-2, 5).

Frequently Asked Questions

What is interval notation?
Interval notation is a way of writing subsets of the real number line. An interval is a set of all real numbers between two given numbers, called the endpoints.
What is the difference between a parenthesis and a bracket?
A parenthesis ( or ) indicates that the endpoint is not included in the interval (an open interval). A bracket [ or ] indicates that the endpoint is included (a closed interval).
How do you write "all real numbers" in interval notation?
The set of all real numbers is written as (-∞, ∞).

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