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Math library functions that return NaN

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Generally, Math functions that are given non-numeric arguments will return NaN. 

Math.floor("a")

The square root of a negative number returns NaN, because Math.sqrt does not support imaginary or complex numbers. 

Math.sqrt(-1)
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Built-in constants:
* null
* undefined and null
* Number constants
* NaN
* Operations that return NaN
* Math library functions that return NaN
* Testing for NaN using isNaN
* Infinity and -Infinity
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