Definition. This function returns the arctangent or inverse tangent of a number.
Argument
number (required) The tangent of the angle you want to calculate
Background. Use the ATAN() function to calculate the adjacent angle based on the tangent (see Figure 16-7). In other words, the arctangent is the angle whose tangent is number. The result is a radian measure between –π/2 and π/2 and has to be converted into degrees with the DEGREES() function or by multiplying the result with 180/PI().
Because each angle occurs two times in a full circle, the value range for an arctangent is restricted.
If the angle is calculated as a radian measure, the value range spans –π/2 to π/2.
If the angle is calculated in degrees, the value range spans –90° to 90°.
The values of the arctangent in a coordinate plane look like those shown in Figure 16-7.
Examples. The ATAN() function is used to calculate the angles of a right triangle based on the opposite leg and the adjacent leg.
In one example, the angle resulting from tangent 1 could be 45º as well as 225º. Because the range is limited to –90º to 90º, the result is 45º. The corresponding formula looks like this:
=DEGREES(ATAN(1))
Because the result is a radian measure, you have to convert it by using the DEGREES() function. More examples for this function are:
=DEGREES(ATAN(–1))returns angle α with –45°.=DEGREES(ATAN(0.75355405))returns angle α with 37°.=DEGREES(ATAN(4.010780934))returns angle α with 76°.