# File lib/eymiha/math3/quaternion.rb, line 233
    def divide!(axis=origin,real=1)
      if axis.kind_of? Quaternion
        divide!(axis.axis,axis.real)
      elsif axis.point3_like?
        multiply!(quaternion(axis,real).inverse!)
      else
        raise_no_conversion axis
      end
      self
    end