BigDecimal cosine - Java java.math

Java examples for java.math:BigDecimal Trigonometric Function

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Description

BigDecimal cosine

Demo Code

/*//from   ww w.  j av a2  s . c  o m
 * 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.
 */
//package com.java2s;
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 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;
    }
}

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