Here you can find the source of acos(float value)
static public final float acos(float value)
//package com.java2s; /**/*from w w w . j a va2 s. c o m*/ * Copyright 2008 - 2011 * * Licensed under the Apache License, Version 2.0 (the "License"); you may not * use this file except in compliance with the License. You may obtain a copy of * the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the * License for the specific language governing permissions and limitations under * the License. * * @project loonframework * @author chenpeng * @email?ceponline@yahoo.com.cn * @version 0.1 */ public class Main { static final int AS1 = -1228; static final int AS2 = 4866; static final int AS3 = 13901; static final int AS4 = 102939; public static int acos(int f) { int fRoot = sqrt((1 << 16) - f); int result = AS1; result = mul(result, f); result += AS2; result = mul(result, f); result -= AS3; result = mul(result, f); result += AS4; result = mul(fRoot, result); return result; } static public final float acos(float value) { return (float) Math.acos(value); } public static int sqrt(int n) { int s = (n + 65536) >> 1; for (int i = 0; i < 8; i++) { s = (s + div(n, s)) >> 1; } return s; } static public final float sqrt(float a) { return (float) Math.sqrt(a); } public static int mul(int x, int y) { long z = (long) x * (long) y; return ((int) (z >> 16)); } public static int div(int x, int y) { long z = (((long) x) << 32); return (int) ((z / y) >> 16); } }