Cosine.java

package ru.itmo.qa.lab2.trig;

import ch.obermuhlner.math.big.BigDecimalMath;
import ru.itmo.qa.lab2.function.AbstractFunction;

import java.math.BigDecimal;
import java.math.MathContext;

import static java.math.RoundingMode.HALF_EVEN;

public class Cosine extends AbstractFunction {

  private final Sine sine;

  public Cosine() {
    super();
    this.sine = new Sine();
  }

  public Cosine(Sine sine) {
    super();
    this.sine = sine;
  }

  @Override
  public BigDecimal calculate(BigDecimal x, BigDecimal precision) throws ArithmeticException {
    isValid(x, precision);

    MathContext mc = new MathContext(precision.scale() + 2, HALF_EVEN);

    BigDecimal piHalf = BigDecimalMath.pi(mc)
        .divide(BigDecimal.valueOf(2), mc.getPrecision(), HALF_EVEN);

    return sine.calculate(piHalf.subtract(x), precision);
  }
}