The expression must evaluate to an approximate numeric data type.
Example
The following example illustrates two ways to use the ATAN function:
select atan (1) * (180/ pi()) 'Arctangent in degrees' from syscalctable;
ARCTANGENT IN DEGREES
-----------------------
45.000000000000000
1 record selected
select atan (1) 'Arctangent in radians' from syscalctable;
ARCTANGENT IN RADIANS
-----------------------
0.785398163397448
1 record selected
ATAN takes the ratio (expression) of two sides of a right triangle and returns the corresponding angle. The ratio is the length of the side opposite the angle divided by the length of the side adjacent to the angle.
The result is expressed in radians and is in the range -Pi/2 to Pi/2 radians. To convert degrees to radians, multiply degrees by Pi/180. To convert radians to degrees, multiply radians by 180/Pi.
The expression must be in the range -1 to 1.