# SIMD.%type%.reciprocalSqrtApproximation()

This is an experimental technology
Because this technology's specification has not stabilized, check the compatibility table for usage in various browsers. Also note that the syntax and behavior of an experimental technology is subject to change in future versions of browsers as the specification changes.

The static `SIMD.%type%.reciprocalSqrtApproximation()` method returns a new instance with an approximation of the reciprocal value (`1 / x`) of the square root (`Math.sqrt()`) of the lane values.

## Syntax

```SIMD.Float32x4.reciprocalSqrtApproximation(t)
SIMD.Float64x2.reciprocalSqrtApproximation(t)```

### Parameters

t
An instance of a corresponding SIMD type.

### Return value

A new corresponding SIMD data type with the reciprocal (`1 / x`) of the square root (`Math.sqrt()`) of the values.

## Description

The `SIMD.%type%.reciprocalSqrtApproximation()` is an approximation of the reciprocal of the square root of the lane values. This means that an estimation of the reciprocal of a number is calculated and that there can be a small amount of error. The Newton-Raphson division, for example, is one of the fast division methods that calculates an estimation. See also this ARM/NEON FAQ article.

## Examples

```var a = SIMD.Float32x4(1, 2, 3, 4);
SIMD.Float32x4.reciprocalSqrtApproximation(a);
// Float32x4[1, 0.7071067690849304, 0.5773502588272095, 0.5]

var b = SIMD.Float64x2(0, Infinity);
SIMD.Float64x2.reciprocalSqrtApproximation(b);
// Float64x2[Infinity, 0]
```

## Specifications

Specification Status Comment
SIMD
The definition of 'SIMDConstructor.reciprocalSqrtApproximation' in that specification.
Draft Initial definition.

## Browser compatibility

Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari
Basic support No support Nightly build No support No support No support
Feature Android Chrome for Android Firefox Mobile (Gecko) IE Mobile Opera Mobile Safari Mobile
Basic support No support No support Nightly build No support No support No support