class PhysicsVector
  def initialize(name,x,y,z)
    @name = name
    @x = x.to_f
    @y = y.to_f
    @z = z.to_f
  end

  def x
    x = @x
  end

  def y
    y = @y
  end

  def z
    z = @z
  end

  def add(n,a)
    return PhysicsVector.new(n,@x + a.x,@y + a.y,@z + a.z)
  end

  def subtract(n,a)
    return PhysicsVector.new(n,@x - a.x,@y - a.y,@z - a.z)
  end

  def print()
    puts @name + " = " + @x.to_s + "i + " + @y.to_s + "j + " + @z.to_s + "k"
  end

  def magnitude()
    return Math.sqrt((@x * @x) + (@y * @y) + (@z * @z))
  end 

  def print_magnitude()
    puts "magnitude of " + @name + " = " + self.magnitude().to_s
  end

  def direction_r()
    return Math.atan2(@y, @x)
  end 

  def direction_d()
    return Math.atan2(@y, @x) * 90.0 / Math.asin(1.0)
  end 

  def print_direction_r()
    puts "direction of " + @name + " in radians = " + self.direction_r().to_s
  end

  def print_direction_d()
    puts "direction of " + @name + " in degrees = " + self.direction_d().to_s
  end

end

# define maim function
def main()
  puts "Ruby output"
  puts "Chapter 2"
  puts "Problem 5"
  a = PhysicsVector.new("a",4.0,-3.0,0.0)
  b = PhysicsVector.new("b",6.0,8.0,0.0)

  c = a.add("c",b)
  d = b.subtract("d",a)
  e = a.subtract("e",b)

  a.print()
  b.print()
  c.print()
  d.print()
  e.print()

  a.print_magnitude()
  b.print_magnitude()
  c.print_magnitude()
  d.print_magnitude()
  e.print_magnitude()

  a.print_direction_r()
  b.print_direction_r()
  c.print_direction_r()
  d.print_direction_r()
  e.print_direction_r()

  a.print_direction_d()
  b.print_direction_d()
  c.print_direction_d()
  d.print_direction_d()
  e.print_direction_d()

end

main()