# System Functions

ATN( ) | Return Arc-Tangent

## Format

ATN(num[,ERR=stmtref])
Where:

num | Numeric expression whose Arc-Tangent is to be returned.
stmtref | Program line number or statement label to which to transfer control.
#### Note: The value to be supplied must be in Radians, not Degrees. To convert Degrees to Radians: Radians = Degrees * pi / 180 Degrees = Radians * 180 / pi

## Returns

Numeric value, range -ð/2 to +ð/2.

## Description

The ATN( ) function returns the Arc-Tangent of the numeric expression num. It will return a value between -ð (negative pi) divided by 2 and ð divided by 2, rounded to the current PRECISION in effect. This is the inverse of the TAN( ) function.

## Example

for I=-10 to 10 step 1
print atn(I),
next
print " DONE"
end
->run
-1.47-1.46-1.45-1.43-1.41-1.37-1.33-1.25-1.11-0.79 0 0.79 1.11 1.25 1.33 1.37 1.41 1.43 1.45 1.46 1.47 DONE