README.md (1801B)
1 <!-- 2 3 @license Apache-2.0 4 5 Copyright (c) 2018 The Stdlib Authors. 6 7 Licensed under the Apache License, Version 2.0 (the "License"); 8 you may not use this file except in compliance with the License. 9 You may obtain a copy of the License at 10 11 http://www.apache.org/licenses/LICENSE-2.0 12 13 Unless required by applicable law or agreed to in writing, software 14 distributed under the License is distributed on an "AS IS" BASIS, 15 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 16 See the License for the specific language governing permissions and 17 limitations under the License. 18 19 --> 20 21 # cosm1 22 23 > Compute `cos(x) - 1`. 24 25 <section class="usage"> 26 27 ## Usage 28 29 ```javascript 30 var cosm1 = require( '@stdlib/math/base/special/cosm1' ); 31 ``` 32 33 #### cosm1( x ) 34 35 Computes `cos(x) - 1`, where `cos` is the [cosine][@stdlib/math/base/special/cos] of a `number` (in radians). This function should be used instead of manually calculating `cos(x) - 1` when the argument is near unity. 36 37 ```javascript 38 var PI = require( '@stdlib/constants/float64/pi' ); 39 40 var v = cosm1( 0.0 ); 41 // returns 0.0 42 43 v = cosm1( PI/4.0 ); 44 // returns ~-0.293 45 46 v = cosm1( -PI/6.0 ); 47 // returns ~-0.134 48 49 v = cosm1( NaN ); 50 // returns NaN 51 ``` 52 53 </section> 54 55 <!-- /.usage --> 56 57 <section class="examples"> 58 59 ## Examples 60 61 <!-- eslint no-undef: "error" --> 62 63 ```javascript 64 var linspace = require( '@stdlib/array/linspace' ); 65 var PI = require( '@stdlib/constants/float64/pi' ); 66 var cosm1 = require( '@stdlib/math/base/special/cosm1' ); 67 68 var x = linspace( 0.0, 2.0*PI, 100 ); 69 var i; 70 71 for ( i = 0; i < x.length; i++ ) { 72 console.log( cosm1( x[ i ] ) ); 73 } 74 ``` 75 76 </section> 77 78 <!-- /.examples --> 79 80 <section class="links"> 81 82 [@stdlib/math/base/special/cos]: https://www.npmjs.com/package/@stdlib/math/tree/main/base/special/cos 83 84 </section> 85 86 <!-- /.links -->