1   /*
2    * Copyright 2003-2004 The Apache Software Foundation.
3    * 
4    * Licensed under the Apache License, Version 2.0 (the "License");
5    * you may not use this file except in compliance with the License.
6    * You may obtain a copy of the License at
7    * 
8    *      http://www.apache.org/licenses/LICENSE-2.0
9    * 
10   * Unless required by applicable law or agreed to in writing, software
11   * distributed under the License is distributed on an "AS IS" BASIS,
12   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13   * See the License for the specific language governing permissions and
14   * limitations under the License.
15   */
16  package org.apache.commons.math.analysis;
17  
18  import org.apache.commons.math.FunctionEvaluationException;
19  
20  /**
21   * Auxillary class for testing solvers.
22   *
23   * The function is extraordinarily well behaved around zero roots: it
24   * has an inflection point there (second order derivative is zero),
25   * which means linear approximation (Regula Falsi) will converge
26   * quadratically.
27   * 
28   * @version $Revision: 155427 $ $Date: 2005-02-26 06:11:52 -0700 (Sat, 26 Feb 2005) $
29   */
30  public class SinFunction implements DifferentiableUnivariateRealFunction {
31  
32      /* Evaluate sinus fuction.
33       * @see org.apache.commons.math.UnivariateRealFunction#value(double)
34       */
35      public double value(double x) throws FunctionEvaluationException {
36          return Math.sin(x);
37      }
38  
39      /* First derivative of sinus function
40       */
41      public UnivariateRealFunction derivative() {
42          return new UnivariateRealFunction() {
43              public double value(double x) throws FunctionEvaluationException {
44                  return Math.cos(x);
45              }
46          };
47      }
48  
49  }