Math.atan()

The Math.atan() static method returns the inverse tangent (in radians) of a number, that is

{{InteractiveExample("JavaScript Demo: Math.atan()")}}

```js interactive-example // Calculates angle of a right-angle triangle in radians function calcAngle(opposite, adjacent) { return Math.atan(opposite / adjacent); }

console.log(calcAngle(8, 10)); // Expected output: 0.6747409422235527

console.log(calcAngle(5, 3)); // Expected output: 1.0303768265243125

## Syntax

```js-nolint
Math.atan(x)

Parameters#

• x
• : A number.

Return value#

The inverse tangent (angle in radians between $-\frac{\pi}{2}$ and $\frac{\pi}{2}$, inclusive) of x. If x is {{jsxref("Infinity")}}, it returns $\frac{\pi}{2}$. If x is -Infinity, it returns $-\frac{\pi}{2}$.

Description#

Because atan() is a static method of Math, you always use it as Math.atan(), rather than as a method of a Math object you created (Math is not a constructor).

Examples#

Using Math.atan()#

Math.atan(-Infinity); // -1.5707963267948966 (-π/2)
Math.atan(-0); // -0
Math.atan(0); // 0
Math.atan(1); // 0.7853981633974483  (π/4)
Math.atan(Infinity); // 1.5707963267948966  (π/2)

// The angle that the line (0,0) -- (x,y) forms with the x-axis in a Cartesian coordinate system
const theta = (x, y) => Math.atan(y / x);

Note that you may want to avoid the theta function and use {{jsxref("Math.atan2()")}} instead, which has a wider range (between -π and π) and avoids outputting NaN for cases such as when x is 0.

Specifications#

{{Specifications}}

Browser compatibility#

{{Compat}}

See also#

• {{jsxref("Math.acos()")}}
• {{jsxref("Math.asin()")}}
• {{jsxref("Math.atan2()")}}
• {{jsxref("Math.cos()")}}
• {{jsxref("Math.sin()")}}
• {{jsxref("Math.tan()")}}
• CSS {{cssxref("atan()")}} function