/**
 * 
 */
package math;

/**
 * @author Link
 *
 */
public class Main {

	private static final double pi180 = Math.PI / 180;

	private static final int T1 = 6, T2 = 120, T3 = 5_040, T4 = 362_880, T5 = 39_916_800;
	private static final long T6 = 6_227_020_800L, T7 = 1_307_674_368_000L, T8 = 355_687_428_096_000L,
			t9 = 121_645_100_408_832_000L;

	public static void main(String... args) {
		long t = System.currentTimeMillis();
		System.out.println("Math.tan(x) = " + Math.tan(pi180 * 140d));
		System.out.println("time (ms): " + (System.currentTimeMillis() - t));
		t = System.currentTimeMillis();
		System.out.println("tangent(x) = " + tan(140d));
		System.out.println("time (ms): " + (System.currentTimeMillis() - t));
		System.out.println("Math.tan(x) = " + Math.tan(pi180 * 135.5d));
		System.out.println("time (ms): " + (System.currentTimeMillis() - t));
		t = System.currentTimeMillis();
		System.out.println("tangent(x) = " + tan(140d));
		System.out.println("time (ms): " + (System.currentTimeMillis() - t));
	}

	/**
	 * Faster sine algorithm. Limit -360 to 360.
	 * 
	 * @param x
	 *            x in radians
	 * @return the sine of x
	 */
	public static double sine(double x) {
		final double x1 = x, x2 = x1 * x1;
		// numerators
		final double n1 = x1 * x2, n2 = n1 * x2, n3 = n2 * x2, n4 = n3 * x2, n5 = n4 * x2, n6 = n5 * x2, n7 = n6 * x2,
				n8 = n7 * x2, n9 = n8 * x2;
		return (x1) - (n1 / T1) + (n2 / T2) - (n3 / T3) + (n4 / T4) - (n5 / T5) + (n6 / T6) - (n7 / T7) + (n8 / T8)
				- (n9 / t9);
	}

	public static double sin(double x) {
		return sine(pi180 * x);
	}

	public static double cosine(double x) {
		return sine(Math.PI / 2 - x);
	}

	public static double cos(double x) {
		return cosine(pi180 * x);
	}

	public static double tangent(double x) {
		return cosine(x) / sine(x);
	}

	public static double tan(double x) {
		return tangent(pi180 * x);
	}
}