Math.atan()

¥Syntax

Math.atan(x)

¥Parameters

x

一个号码。

¥Return value

反正切（ x。如果 x 是 Infinity，则返回 $\frac{\pi}{2}$x 是 -Infinity，则返回

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

¥Description

因为 atan() 是 Math 的静态方法，所以你始终将其用作 Math.atan()，而不是用作你创建的 Math 对象的方法（Math 不是构造函数）。

¥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);

请注意，你可能希望避免使用 theta 函数并使用 Math.atan2()，它具有更宽的范围（在 -π 和 π 之间），并避免在 x 为 0 等情况下输出 NaN。

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

¥See also

• Math.acos()
• Math.asin()
• Math.atan2()
• Math.cos()
• Math.sin()
• Math.tan()