86 lines
1.7 KiB
Markdown
86 lines
1.7 KiB
Markdown
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@license Apache-2.0
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Copyright (c) 2018 The Stdlib Authors.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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-->
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# cospi
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> Compute the [cosine][@stdlib/math/base/special/cos] of a number times [π][@stdlib/constants/float64/pi].
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<section class="usage">
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## Usage
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```javascript
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var cospi = require( '@stdlib/math/base/special/cospi' );
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```
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#### cospi( x )
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Computes `cos(πx)` more accurately than `cos(pi*x)`, especially for large `x`.
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```javascript
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var y = cospi( 0.0 );
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// returns 1.0
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y = cospi( 0.5 );
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// returns 0.0
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y = cospi( 0.1 );
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// returns ~0.951
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y = cospi( NaN );
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// returns NaN
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```
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</section>
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<!-- /.usage -->
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<section class="examples">
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## Examples
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<!-- eslint no-undef: "error" -->
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```javascript
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var linspace = require( '@stdlib/array/linspace' );
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var cospi = require( '@stdlib/math/base/special/cospi' );
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var x = linspace( -100.0, 100.0, 100 );
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var i;
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for ( i = 0; i < x.length; i++ ) {
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console.log( cospi( x[ i ] ) );
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}
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```
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</section>
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<!-- /.examples -->
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<section class="links">
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[@stdlib/math/base/special/cos]: https://www.npmjs.com/package/@stdlib/math/tree/main/base/special/cos
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[@stdlib/constants/float64/pi]: https://www.npmjs.com/package/@stdlib/constants-float64-pi
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</section>
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<!-- /.links -->
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