Returns a Double specifying the arctangent of a number.
The required number argument is a Double or any valid numeric expression.
The Atn function takes the ratio of two sides of a right triangle (number) and returns the corresponding angle in radians. The ratio is the length of the side opposite the angle divided by the length of the side adjacent to the angle.
[NOTE!] This is the equivalent of the ATAN() function in Excel. Oddly, Excel.WorksheetFunctions.ATAN() does not exist (as with other Excel formula functions). You can instead use this VBA Atn() function.
The range of the result is -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.
Atn is the inverse trigonometric function of Tan, which takes an angle as its argument and returns the ratio of two sides of a right triangle. Do not confuse Atn with the cotangent, which is the simple inverse of a tangent (1/tangent).