The java.lang.Math.acos() returns the arc cosine of an angle in between 0.0 and pi. Arc cosine is also called as inverse of a cosine.If the argument is NaN or its absolute value is greater than 1, then the result is NaN.
Syntax :
public static double acos(double a) Parameter : a : the value whose arc cosine is to be returned. Return : This method returns the arc cosine of the argument.
Example :To show working of java.lang.Math.acos() method.
// Java program to demonstrate working// of java.lang.Math.acos() methodimport java.lang.Math;  class Gfg {      // driver code    public static void main(String args[])    {        double a = Math.PI;          // Output is NaN, because Math.PI gives 3.141 value        // greater than 1        System.out.println(Math.acos(a));          // convert Math.PI to radians        double b = Math.toRadians(a);          System.out.println(Math.acos(b));          double c = 1.0;        double d = 0.0;        double e = -1.0;        double f = 1.5;          System.out.println(Math.acos(c));        System.out.println(Math.acos(d));        System.out.println(Math.acos(e));          // value of f does not lie in between -1 and 1        // so output is NaN        System.out.println(Math.acos(f));    }} |
Output:
NaN 1.5159376794536454 0.0 1.5707963267948966 3.141592653589793 NaN
