Java BigDecimal tangent(BigDecimal x)

Description

tangent

License

Apache License

Declaration

public static BigDecimal tangent(BigDecimal x) 

Method Source Code

//package com.java2s;
/*//  ww w  .ja v a 2 s  .co  m
 * $Id$
 *
 * Copyright 2013 Valentyn Kolesnikov
 *
 * 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.
 */

import java.math.BigDecimal;

public class Main {
    private static final int SCALE = 18;
    private static final int ROUNDING_MODE = BigDecimal.ROUND_HALF_EVEN;

    public static BigDecimal tangent(BigDecimal x) {

        BigDecimal sin = sine(x);
        BigDecimal cos = cosine(x);

        return sin.divide(cos, SCALE, BigDecimal.ROUND_HALF_UP);
    }

    public static BigDecimal sine(BigDecimal x) {
        BigDecimal lastVal = x.add(BigDecimal.ONE);
        BigDecimal currentValue = x;
        BigDecimal xSquared = x.multiply(x);
        BigDecimal numerator = x;
        BigDecimal denominator = BigDecimal.ONE;
        int i = 0;

        while (lastVal.compareTo(currentValue) != 0) {
            lastVal = currentValue;

            int z = 2 * i + 3;

            denominator = denominator.multiply(BigDecimal.valueOf(z));
            denominator = denominator.multiply(BigDecimal.valueOf(z - 1));
            numerator = numerator.multiply(xSquared);

            BigDecimal term = numerator.divide(denominator, SCALE + 5, ROUNDING_MODE);

            if (i % 2 == 0) {
                currentValue = currentValue.subtract(term);
            } else {
                currentValue = currentValue.add(term);
            }

            i++;
        }
        return currentValue;
    }

    public static BigDecimal cosine(BigDecimal x) {

        BigDecimal currentValue = BigDecimal.ONE;
        BigDecimal lastVal = currentValue.add(BigDecimal.ONE);
        BigDecimal xSquared = x.multiply(x);
        BigDecimal numerator = BigDecimal.ONE;
        BigDecimal denominator = BigDecimal.ONE;
        int i = 0;

        while (lastVal.compareTo(currentValue) != 0) {
            lastVal = currentValue;

            int z = 2 * i + 2;

            denominator = denominator.multiply(BigDecimal.valueOf(z));
            denominator = denominator.multiply(BigDecimal.valueOf(z - 1));
            numerator = numerator.multiply(xSquared);

            BigDecimal term = numerator.divide(denominator, SCALE + 5, ROUNDING_MODE);

            if (i % 2 == 0) {
                currentValue = currentValue.subtract(term);
            } else {
                currentValue = currentValue.add(term);
            }
            i++;
        }

        return currentValue;
    }
}

Related

1. stripTrailingZeros(BigDecimal bigDecimal)
2. stripTrailingZeros(BigDecimal value)
3. stripTrailingZeros(final BigDecimal decimal)
4. strToBigDecimal(final String arg)
5. strValueBigDecimal(Number number)
6. tanto(BigDecimal r, BigDecimal n)
7. textToBigDecimal(String amountAsText)
8. transferDonateAmount2Point(BigDecimal donateAmount)
9. tryParseBigDecimal(Object val, BigDecimal defaultVal)