# ISO 80000-2

ISO 80000-2:2009 is a standard describing mathematical signs and symbols developed by the International Organization for Standardization (ISO), superseding ISO 31-11. The Standard, whose full name is Quantities and units – Part 2: Mathematical signs and symbols to be used in the natural sciences and technology, is a part of the group of standards called ISO/IEC 80000.

## Contents list

The Standard is divided into the following chapters:

• Foreword
• Introduction
1. Scope
2. Normative references
3. Variables, functions, and operators
4. Mathematical logic
5. Sets
6. Standard number sets and intervals
7. Miscellaneous signs and symbols
8. Elementary geometry
9. Operations
10. Combinatorics
11. Functions
12. Exponential and logarithmic functions
13. Circular and hyperbolic functions
14. Complex numbers
15. Matrices
16. Coordinate systems
17. Scalars, vectors, and tensors
18. Transforms
19. Special functions
• Annex A (normative) - Clarification of the symbols used
• Bibliography

## Symbols for variables and constants

Clause 3 specifies that variables such as x and y, and functions in general (e.g., ƒ(x)) are printed in italic type, while mathematical constants and functions that do not depend on the context (e.g., sin(x + π)) are in roman (upright) type. Examples given of mathematical (upright) constants are e, π and i. The numbers 1, 2, 3, etc. are also upright.

## Additions to ISO 31-11

Examples of additions at an elementary level are the inclusions of int a for the integer part of a real number, frac a for the fractional part of a real number and P (often typeset as blackboard bold ) for the set of primes.

## Function symbols and definitions

Clause 13 defines trigonometric and hyperbolic functions such as sin and tanh and their respective inverses arcsin and artanh. The popular way of writing these inverses as sin−1 and tanh−1 is not included in ISO 80000-2.

1. ^ "ISO 80000-2:2009". International Organization for Standardization. Retrieved 1 July 2010.