Get the sine of an angle - Java java.lang

Java examples for java.lang:Math Trigonometric Function

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Description

Get the sine of an angle

Demo Code


//package com.java2s;

public class Main {
    /**//from w w  w  .  j a  v a 2 s.  c o m
     * Get the sine of an angle
     * 
     * @param radians The angle
     * @return The sine of the angle
     * @author JeffK
     */
    public static double sin(double radians) {
        radians = reduceSinAngle(radians); // limits angle to between -PI/2 and +PI/2
        if (Math.abs(radians) <= Math.PI / 4) {
            return Math.sin(radians);
        } else {
            return Math.cos(Math.PI / 2 - radians);
        }
    }

    /**
     * Fast Trigonometry functions for x86.  
     * This forces the trigonometry functions to stay within the safe area on the x86 processor (-45 degrees to +45 degrees)
     * The results may be very slightly off from what the Math and StrictMath trigonometry functions give due to
     * rounding in the angle reduction but it will be very very close.
     * 
     * @param radians The original angle
     * @return The reduced Sin angle
     * @author JeffK
     */
    private static double reduceSinAngle(double radians) {
        radians %= Math.PI * 2.0; // put us in -2PI to +2PI space

        if (Math.abs(radians) > Math.PI) { // put us in -PI to +PI space
            radians = radians - (Math.PI * 2.0);
        }
        if (Math.abs(radians) > Math.PI / 2) {// put us in -PI/2 to +PI/2 space
            radians = Math.PI - radians;
        }

        return radians;
    }

    /**
     * Get the cosine of an angle
     * 
     * @param radians The angle
     * @return The cosine of the angle
     * @author JeffK
     */
    public static double cos(double radians) {
        return sin(radians + Math.PI / 2);
    }
}

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