java.lang.Math.acos(double a) java.lang.Math.abs(long a) java.lang.Math.asin(double a) java.lang.Math.acos(double a) package com.codingdict; import java.lang.*; public class MathDemo { public static void main(String[] args) { // get a variable x which is equal to PI/2 double x = Math.PI / 2; // convert x to radians x = Math.toRadians(x); // get the arc cosine of x System.out.println("Math.acos(" + x + ")=" + Math.acos(x)); } } java.lang.Math.abs(long a) java.lang.Math.asin(double a)