Related Functions:

The ATAN function returns the arctangent, or inverse tangent, of a number. The arctangent is the angle whose tangent is number. The returned angle is given in radians in the range -\pi/2 to \pi/2.

Syntax

=ATAN(number)

Arguments

Argument Description
number The tangent of the angle you want

Examples

  A B C
1 Formula Result Notes
2 =ATAN(-1) -0.785398163 Arctangent of -1 in radians, -pi/4
3 =ATAN(1) 0.785398163 Arctangent of 1 in radians, pi/4
4 =ATAN(1)*180/PI() 45 Arctangent of 1 in degrees
5 =DEGREES(ATAN(1)) 45 Arctangent of 1 in degrees

Note: If you want the angle returned by the ATAN function to be expressed in degrees, you can convert it, using the DEGREES function: =DEGREES(radians)

Common Function Error(s)

Problem What went wrong
#VALUE! Occurs if the supplied number argument is not recognized as a numeric value

trigonometry_triangleThe arctangent is the inverse of the tangent. Therefore, for the simple right-angle triangle at right, the arctangent of the opposite side (a), divided by the adjacent side (b), is equal to the angle A. Arctangent is calculated as:  

    \[   A = arctan \left( \frac{a}b \right)    \]

See Wikipedia for more information on Inverse Trigonometric Functions.