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

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 $-\frac{\pi}{2}$ and $\frac{\pi}{2}$, 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 (-π/2)
Math.asin(-0); // -0
Math.asin(0); // 0
Math.asin(0.5); // 0.5235987755982989 (π/6)
Math.asin(1); // 1.5707963267948966 (π/2)
Math.asin(2); // NaN

Specifications

Browser compatibility

See also

• Math.acos()
• Math.atan()
• Math.atan2()
• Math.cos()
• Math.sin()
• Math.tan()
• CSS asin() function