# Documentation/Calc Functions/ATAN

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ATAN

Mathematical

## Summary:

Calculates the inverse trigonometric tangent (arctangent or arctan) of a real number. The value returned is the principal value and lies in the range (-π/2, π/2) radians.

ATAN(Number)

## Returns:

Returns a real number in the range (-π/2, π/2) that is the inverse trigonometric tangent of Number in radians.

## Arguments:

Number is a real number, or a reference to a cell containing that number, whose inverse trigonometric tangent is to be calculated.

• If Number is non-numeric, then ATAN reports a #VALUE! error.

• To return the angle in degrees, use the DEGREES function.
• Alternatively multiply by 180/PI() to convert the result from radians to degrees.

The figure below illustrates the function ATAN.

## Examples:

Formula Description Returns
=ATAN(-1) Inverse trigonometric tangent of -1. -0.785398163397448 (-π/4)
=ATAN(D1) where cell D1 contains the number 0.5. Inverse trigonometric tangent of 0.5. 0.463647609000806
=DEGREES(ATAN(0.5)) Inverse trigonometric tangent of 0.5, converted to degrees. 26.565051177078
=ATAN(-0.5)*180/PI() Inverse trigonometric tangent of -0.5, converted to degrees. -26.565051177078
=DEGREES(ATAN(TAN(RADIANS(60))) An angle of 60° is converted to radians, its tangent is taken, then the inverse tangent of that value is calculated, and finally the result is converted back to degrees. 60

ATAN