# How to use the ATAN function

**What is the ATAN function?**

The ATAN function calculates the arctangent of a number. The returned angle is in radians between -pi/2 to pi/2.

**What is the trigonometric tangent?**

The tangent is a trigonometric function that relates an angle θ in a right triangle to the ratio of the length of the side opposite the angle and the length of the adjacent side of the triangle. A right triangle has one angle that measures 90° or π/2 radians which is approximately 1.5707963267949 radians.

**What is the angle θ?**

The Greek letter theta (θ) is commonly used to represent an unknown angle in a right triangle.

**What is a right triangle?**

A right triangle is a type of triangle that contains one internal angle measuring 90 degrees or π/2 radians (a right angle).

**What are radians?**

Radians are a unit used to measure angles. An angle of 1 radian has an arc length equal to the circle's radius.

**What is the relationship between the number pi and radians?**

Radians measure angles by the length of the arc they make in a circle rather than degrees. The full circumference of any circle is 2π multiplied by the circle's radius (2πr).

Since the circumference goes all the way around a circle, that means the full circle measures 2π radians. Half a circle would be π radians (half of 2π). A quarter circle is 2π/4 = π/2 radians. An eighth of a circle is 2π/8 = π/4 radians.

Excel has a function that returns the number pi: PI function

**What are degrees?**

Degrees are a unit used to measure angles. It is based on dividing a full circle into 360 equal parts. Degrees are divided into fractional parts like minutes and seconds for more precision.

**What is the relationship between radians and degrees?**

The circumference of a circle is 360 degrees or 2π radians.

360 degrees = 2π radians

which is

degrees = radians x (180 / π)

Excel has two functions for converting between radians and degrees: RADIANS | DEGREES

**What is the arctangent?**

The ATAN function calculates the the angle is in radians based on the ratio between the opposite side and the adjacent side, it is often displayed as TAN^{-1} in scientific calculators.

**What is an arc?**

An arc is a curved segment of a circle's circumference, it is a portion of the circle's curve, defined by two endpoints.

In other words, an arc is formed by two radii intersecting the circumference and the enclosed edge between them.

**What is a circle's radius?**

The radius of a circle is the distance from the center point to any point on the circle's edge or circumference.

**What is radii?**

The plural form of the word "radius".

**What is the radius of a circle?**

The radius of a circle is the distance from the center point to any point on the circle's edge or circumference.

### Excel Function Syntax

ATAN(*number*)

### Arguments

number |
Required. The tangent of the angle. |

=ATAN(B3)

### Comments

Use the DEGREES function to convert radians to degrees.

=DEGREES(ATAN(-1))

Recommended articles

What is the DEGREES function? The DEGREES function calculates degrees based on radians. What is degree? Degrees are a unit […]

### Functions in 'Math and trigonometry' category

The ATAN function function is one of 73 functions in the 'Math and trigonometry' category.

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