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A question on plotting functions on a graph

  1. Dec 30, 2015 #1
    when i was reading a supplementary notes doc from open course ware fro MIT on single variable calculus there was a description about a graphical representation of a single valued function as
    " if each line parallel to the y- axis and which passes through a point in the domain intersects the graph at only one point then our function is single valued " my point is since it is a line drawn parallel to the y- axis for each input there will be several outputs ,therefore how come it is a function at all?
  2. jcsd
  3. Dec 30, 2015 #2
    It is not function. It is just a line.
  4. Dec 30, 2015 #3


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    Science Advisor
    Homework Helper

    It's nothing more than a question of terminology.
    Currently a function is defined as single valued. In certain applications one uses the concept multivalued functions (complex logarithm for example).

    Apparently our current definition of function has changed with time.

    From Wikipedia:
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