Returns the arctangent of a number in radians
(atan num1 [num2])
Arguments
A number.
A number.
Return Values
The arctangent of num1, in radians, if only num1 is supplied. If you supply both num1 and num2 arguments, atan returns the arctangent of num1/num2, in radians. If num2 is zero, it returns an angle of plus or minus 1.570796 radians (+90 degrees or -90 degrees), depending on the sign of num1. The range of angles returned is -pi/2 to +pi/2 radians.
Examples
Command: (atan 1)
0.785398
Command: (atan 1.0)
0.785398
Command: (atan 0.5)
0.463648
Command: (atan 1.0)
0.785398
Command: (atan -1.0)
-0.785398
Command: (atan 2.0 3.0)
0.588003
Command: (atan 2.0 -3.0)
2.55359
Command: (atan 1.0 0.0)
1.5708
