HP 39G User Manual page 142

ABS
n
10-6
Power (x raised to y). Also accepts complex numbers.
value^power
Example
2^8 returns 256
Absolute value. For a complex number, this is
ABS(value)
ABS((x , y))
Example
ABS(–1) returns 1
ABS((1,2)) returns 2.2360679775
Takes the nth root of x.
root NTHROOT value
Example
3 NTHROOT 8 returns 2
2 2
x + y .
Using mathematical functions