src/test/org/apache/commons/math/analysis/SinFunction.java

/*
 * Copyright 2003-2004 The Apache Software Foundation.
 * 
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.commons.math.analysis;

import org.apache.commons.math.FunctionEvaluationException;

/**
 * Auxillary class for testing solvers.
 *
 * The function is extraordinarily well behaved around zero roots: it
 * has an inflection point there (second order derivative is zero),
 * which means linear approximation (Regula Falsi) will converge
 * quadratically.
 * 
 * @version $Revision$ $Date$
 */
public class SinFunction implements DifferentiableUnivariateRealFunction {

    /* Evaluate sinus fuction.
     * @see org.apache.commons.math.UnivariateRealFunction#value(double)
     */
    public double value(double x) throws FunctionEvaluationException {
        return Math.sin(x);
    }

    /* First derivative of sinus function
     */
    public UnivariateRealFunction derivative() {
        return new UnivariateRealFunction() {
            public double value(double x) throws FunctionEvaluationException {
                return Math.cos(x);
            }
        };
    }

}