Intuitively, {{CMD_37}} the {{CMD_38}} of {{MATH_39}} as {{MATH_40}} approaches {{MATH_41}} is {{MATH_42}}, {{CMD_43}} written {{MATH_44}} if the value of {{MATH_45}} is as close as one wishes to {{MATH_46}} for all {{MATH_47}} sufficiently close, but not equal to, {{MATH_48}}. {{CMD_49}}