| ATN( ) | Return Arc-Tangent | 
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: | |
Numeric value, range -ð/2 to +ð/2.
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.
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