ATAN function
ATAN returns the inverse trigonometric tangent of a number.
Syntax
ATAN (number)
This function returns the inverse trigonometric tangent of number, which is the angle (in radians) whose tangent is Number. The angle returned is between -PI/2 and PI/2.
Example
=ATAN(1) returns 0.785398163397448 (PI/4 radians)..
=DEGREES(ATAN(1)) returns 45. The tangent of 45 degrees is 1.