Math.acos()
Baseline Widely available
This feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2015.
Math.acos()
靜態方法會回傳一個數值的反餘弦值(以弧度表示)。也就是說,
嘗試一下
// Calculates angle of a right-angle triangle in radians
function calcAngle(adjacent, hypotenuse) {
return Math.acos(adjacent / hypotenuse);
}
console.log(calcAngle(8, 10));
// Expected output: 0.6435011087932843
console.log(calcAngle(5, 3));
// Expected output: NaN
語法
js
Math.acos(x)
參數
x
-
一個介於 -1 和 1(包含邊界)的數字,代表角度的餘弦值。
回傳值
x
的反餘弦值(0 到 π 之間的角度,以弧度表示,包含邊界)。如果 x
小於 -1 或大於 1,則回傳 NaN
。
描述
由於 acos()
是 Math
的靜態方法,你必須使用 Math.acos()
來呼叫它,而非呼叫你建立的 Math
物件的方法(Math
並非建構子)。
範例
使用 Math.acos()
js
Math.acos(-2); // NaN
Math.acos(-1); // 3.141592653589793 (π)
Math.acos(0); // 1.5707963267948966 (π/2)
Math.acos(0.5); // 1.0471975511965979 (π/3)
Math.acos(1); // 0
Math.acos(2); // NaN
規範
Specification |
---|
ECMAScript® 2025 Language Specification # sec-math.acos |
瀏覽器相容性
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