This function calculates the arctangent, that is, the angle whose tangent is the specified value.
ATAN(value)
For the argument, specify the tangent of the angle you want to return, which must be a value between –1 and 1.
The result angle is in radians between –PI/2 and PI/2. If you want to convert the result to degrees, multiply the result by 180/PI.
Accepts numeric data. Returns numeric data.
ATAN(B3)
ATAN(R3C2)
ATAN(1) gives the result 0.7853981634