Math.asin()

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The Math.asin() static method returns the inverse sine (in radians) of a number. That is,

x[1,1],.()=arcsin(x)=the unique y[2,2] such that sin(y)=x\forall x \in [{-1}, 1],\;\mathtt{\operatorname{Math.asin}(x)} = \arcsin(x) = \text{the unique } y \in \left[-\frac{\pi}{2}, \frac{\pi}{2}\right] \text{ such that } \sin(y) = x

Try it

// Calculates angle of a right-angle triangle in radians
function calcAngle(opposite, hypotenuse) {
  return Math.asin(opposite / hypotenuse);
}

console.log(calcAngle(6, 10));
// Expected output: 0.6435011087932844

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

Syntax

Math.asin(x)

Parameters

x: A number between -1 and 1, inclusive, representing the angle's sine value.

Return value

The inverse sine (angle in radians between -2-\frac{\pi}{2} and 2\frac{\pi}{2}, inclusive) of x. If x is less than -1 or greater than 1, returns NaN.

Description

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

Examples

Using Math.asin()

Math.asin(-2); // NaN
Math.asin(-1); // -1.5707963267948966 (-/2)
Math.asin(-0); // -0
Math.asin(0); // 0
Math.asin(0.5); // 0.5235987755982989 (/6)
Math.asin(1); // 1.5707963267948966 (/2)
Math.asin(2); // NaN