acosh.js (1427B)
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 arccosine of a number. 33 * 34 * @param {number} x - input value 35 * @returns {number} hyperbolic arccosine (in radians) 36 * 37 * @example 38 * var v = acosh( 1.0 ); 39 * // returns 0.0 40 * 41 * @example 42 * var v = acosh( 2.0 ); 43 * // returns ~1.317 44 * 45 * @example 46 * var v = acosh( NaN ); 47 * // returns NaN 48 */ 49 function acosh( x ) { 50 if ( x < 1.0 ) { 51 return NaN; 52 } 53 if ( isnan( x ) || isinfinite( x ) ) { 54 return x; 55 } 56 return ln( x + (sqrt( x+1.0 )*sqrt( x-1.0 )) ); 57 } 58 59 60 // EXPORTS // 61 62 module.exports = acosh;