代数几何:点,线,抛物线,圆,球,弧度和角度

function Point2D(x, y){
  this.x = x
  this.y = y
}

function Point3D(x, y, z){
  this.x = x
  this.y = y
  this.z = z
}

/* 
 *@param {Point2D} p1
 *@param {Point2D} p2
 *@return {number}
 */
function distance2D(p1, p2){
  var dX = p1.x - p2.x
    , dY = p1.y - p2.y
  return Math.sqrt(Math.pow(dX, 2) + Math.pow(dY, 2))
}

/* 
 *@param {Point3D} p1
 *@param {Point3D} p2
 *@return {number}
 */
function distance3D(p1, p2){
  var dX = p1.x - p2.x
    , dY = p1.y - p2.y
    , dZ = p1.z - p2.z
  return Math.sqrt(Math.pow(dX, 2) + Math.pow(dY, 2) + Math.pow(dZ, 2))
}

if (slope1 === slope2){
  console.log("A与B平行")
 
  if (b1 === b2)
     console.log("A与B重合")
}
else{
  console.log("A与B相交")

  if (-1 === slope1 * slope2)
    console.log("A与B相互垂直")
}

/*
 * @constructor
 * @param {Point2D} point 圆心坐标
 * @param {number} r 半径
 */
function Circle(point, r){
  this.point = point
  this.r = r
}

/*
 *@param {Circle} c1
 *@param {Circle} c2
 *@return {boolean}
 */
function isHit(c1, c2){
  var dCenter = Math.sqrt(Math.pow(c1.center.x - c2.center.x, 2) + Math.pow(c1.center.y - c2.center.y, 2))
  var totalRadius = c1.r + c2.r

  return dCenter <= totalRadius
}

/*
 *@param {Point3D} center
 *@param {number} r
 */
function Sphere(center, r){
  this.center = center
  this.radius = r
}

/*
 *@param {Sphere} c1
 *@param {Sphere} c2
 *@return {boolean}
 */
function isHit(c1, c2){
  var dCenter = Math.sqrt(Math.pow(c1.center.x - c2.center.x, 2) + Math.pow(c1.center.y - c2.center.y, 2) + Math.pow(c1.center.z - c2.center.z, 2))
  var totalRadius = c1.r + c2.r

  return dCenter <= totalRadius
}

function getDegree(radian){
  return radian * 180 / Math.PI
}

function getRadian(degree){
  return degree * Math.PI / 180
}