# BPFK Section: Mathematical Constants

*This page is imported from version 18 of the page BPFK Section: Mathematical Constants from the lojban Tiki.*

### cmavo xo (PA5)

#### Proposed Definition

Number question. A question word to which the answer is a number.

#### Proposed Tag

#### See Also

- {ma}

#### Proposed Keywords

- what number?
- how many?

#### Usage Examples

- xo gerku cu xabju lo zdani be do
*How many dogs live in your house?*

#### Notes

#### Issues

### cmavo ci'i (PA5)

#### Proposed Definition

Infinity. When followed by a number, it denotes a transfinite cardinal, such as ℵ_{0}.

#### Proposed Tag

#### See Also

- {cimni}

#### Proposed Keywords

- infinity

#### Usage Examples

- ci'i da mulna'usle
*There are infinitely many prime numbers.*

#### Notes

#### Issues

As multiplication and exponentiation of transfinite ordinals is incompatible with that of cardinals, a new cmavo should be added for a transfinite ordinal, such as ω_{0}.

### cmavo ka'o (PA5)

#### Proposed Definition

*i*, imaginary unit. When followed by a real number, multiplies that number by i. If four real numbers are separated by three *ka'o*, the number is a quaternion, with the components in the order 1, i, j, k.

#### Proposed Tag

#### See Also

#### Proposed Keywords

- imaginary number
- imaginary i

#### Usage Examples

- saclu fi'ure loi lujna'u li paka'opa .iku'i saclu piro loi lujna'u li ni'upaka'opa
*Only half the complex numbers can be represented in base 1+i, but all complex numbers can be represented in base i-1.*

#### Notes

#### Issues

### cmavo pai (PA5)

#### Proposed Definition

The mathematical constant Pi (π), the ratio of a circle's circumference to its diameter.

#### Proposed Tag

#### See Also

- {te'o}

#### Proposed Keywords

- pi
- π

#### Usage Examples

- li pai du li ji'i ci pi pa vo pa xa
*Pi is approximately equal to 3.1416.*

#### Notes

#### Issues

### cmavo te'o (PA5)

#### Proposed Definition

*e* (ℯ), Euler's number

#### Proposed Tag

#### See Also

- {pai}

#### Proposed Keywords

- Euler's number
- mathematical constant

#### Usage Examples

- li te'o te'a ka'o bi'e pi'i pai su'i pa du li no
- '
**e**i^{}**𝜋+1=0*

#### Notes

#### Issues

### cmavo tu'o (PA5)

#### Proposed Definition

Null operand. A placeholder digit used in MEX operations that are grammatically binary, but semantically unary.

#### Proposed Tag

#### See Also

- {zi'o}

#### Proposed Keywords

- null operand
- placeholder digit

#### Usage Examples

- li fu'a ciboi muboi vu'u du li fu'a reboi tu'o va'a
*3 5 - in reverse polish notation equals the negative of 2*