## (“Unknown”)

'?'## HP49/50 only

Keyboard Access: ALPHA-RS-3

“Undefined” constant function.Also known as “Not a Number” or “NaN”.is a constant which means “not a number” or “undefined”. This is different from “infinity” which means “growing without bound”. The IEEE symbol for is NaN. The HP49/50 yields whenever the result of an exact calculation is not mathematically determinable, e.g. 0/0 in exact mode. is a kind of mathematical black hole; when used as an input to any calculation, the result should always be .

Examples (Exact Mode only!):

1 0 / (infinity) 0 0 / (undefined) 0 0 ^ (the mantissa of infinity is unknown) (the exponent of infinity is infinite)See also: .BYTES:

: 5.5

: 10.5

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