1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one or more
3    * contributor license agreements.  See the NOTICE file distributed with
4    * this work for additional information regarding copyright ownership.
5    * The ASF licenses this file to You under the Apache License, Version 2.0
6    * (the "License"); you may not use this file except in compliance with
7    * the License.  You may obtain a copy of the License at
8    * 
9    *      http://www.apache.org/licenses/LICENSE-2.0
10   * 
11   * Unless required by applicable law or agreed to in writing, software
12   * distributed under the License is distributed on an "AS IS" BASIS,
13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14   * See the License for the specific language governing permissions and
15   * limitations under the License.
16   */
17  package org.apache.commons.math.analysis;
18  
19  import org.apache.commons.math.FunctionEvaluationException;
20  
21  /**
22   * Auxillary class for testing solvers.
23   *
24   * The function is extraordinarily well behaved around zero roots: it
25   * has an inflection point there (second order derivative is zero),
26   * which means linear approximation (Regula Falsi) will converge
27   * quadratically.
28   * 
29   * @version $Revision: 799857 $ $Date: 2009-08-01 09:07:12 -0400 (Sat, 01 Aug 2009) $
30   */
31  public class SinFunction implements DifferentiableUnivariateRealFunction {
32  
33      /* Evaluate sinus fuction.
34       * @see org.apache.commons.math.UnivariateRealFunction#value(double)
35       */
36      public double value(double x) throws FunctionEvaluationException {
37          return Math.sin(x);
38      }
39  
40      /* First derivative of sinus function
41       */
42      public UnivariateRealFunction derivative() {
43          return new UnivariateRealFunction() {
44              public double value(double x) throws FunctionEvaluationException {
45                  return Math.cos(x);
46              }
47          };
48      }
49  
50  }