asinh.js (1568B)
1 /** 2 * @license Apache-2.0 3 * 4 * Copyright (c) 2018 The Stdlib Authors. 5 * 6 * Licensed under the Apache License, Version 2.0 (the "License"); 7 * you may not use this file except in compliance with the License. 8 * You may obtain a copy of the License at 9 * 10 * http://www.apache.org/licenses/LICENSE-2.0 11 * 12 * Unless required by applicable law or agreed to in writing, software 13 * distributed under the License is distributed on an "AS IS" BASIS, 14 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 15 * See the License for the specific language governing permissions and 16 * limitations under the License. 17 */ 18 19 'use strict'; 20 21 // MODULES // 22 23 var isinfinite = require( './../../../../../base/assert/is-infinite' ); 24 var isnan = require( './../../../../../base/assert/is-nan' ); 25 var ln = require( './../../../../../base/special/ln' ); 26 var sqrt = require( './../../../../../base/special/sqrt' ); 27 28 29 // MAIN // 30 31 /** 32 * Computes the hyperbolic arcsine of a number. 33 * 34 * @param {number} x - input value 35 * @returns {number} hyperbolic arcsine (in radians) 36 * 37 * @example 38 * var v = asinh( 0.0 ); 39 * // returns 0.0 40 * 41 * @example 42 * var v = asinh( 2.0 ); 43 * // returns ~1.444 44 * 45 * @example 46 * var v = asinh( -2.0 ); 47 * // returns ~-1.444 48 * 49 * @example 50 * var v = asinh( NaN ); 51 * // returns NaN 52 */ 53 function asinh( x ) { 54 if ( 55 x === 0.0 || // +-0.0 56 isnan( x ) || 57 isinfinite( x ) 58 ) { 59 return x; 60 } 61 if ( x > 0 ) { 62 return ln( x + sqrt( (x*x) + 1 ) ); 63 } 64 // Better precision for large negative `x`: 65 return -ln( -x + sqrt( (x*x) + 1 ) ); 66 } 67 68 69 // EXPORTS // 70 71 module.exports = asinh;