# File lib/eymiha/math3/point3.rb, line 253
    def cross!(x=1/sqrt3,y=1/sqrt3,z=1/sqrt3)
      if x.kind_of? Numeric
        set((@y*z)-(@z*y), (@z*x)-(@x*z), (@x*y)-(@y*x))
      elsif x.point3_like?
        if y.kind_of? Numeric
          cross! x.x, x.y, x.z
        elsif y.point3_like?
          set(x).cross!(y)
        else
          raise_no_conversion y
        end
      else
        raise_no_conversion x
      end
    end