    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: 1.13 $ $Date: 2004/07/17 21:19:39 $
    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  }