When is a polygon not a polygon?

[paulb203]

TL;DR Summary

When it's a frequency polygon?

For a shape to qualify as a polygon does it have to be closed. I was just introduced to frequency polygons and was surprised to see each one was a shape that wasn't closed. The definitions of polygon that I've come across go something like, a closed shape consisting of three or more lines.

 

[phinds]

"polygon" and "frequency polygon" really have nothing to do with each other.

 

[A.T.]

I was just introduced to frequency polygons and was surprised to see each one was a shape that wasn't closed.

The "frequency polygon" is just a fancy name for a line graph of discrete values. It is a polygonal chain, rather than a polygon:
https://en.wikipedia.org/wiki/Polygonal_chain

 

[PeroK]

A polygon is not a polygon when it's a n-gon.

 

[paulb203]

The "frequency polygon" is just a fancy name for a line graph of discrete values. It is a polygonal chain, rather than a polygon:
https://en.wikipedia.org/wiki/Polygonal_chain

Thanks. I'll now think of them as Frequency Polygonal Chains. I might even annoy my maths teacher by correcting her :)

 

[pbuk]

The "frequency polygon" is just a fancy name for a line graph of discrete values.

Who on Earth invented this nonsense? I am shocked to see that it is part of the (GCSE) syllabus in the UK, when did that happen?

It is idiocy to confuse students by using the word "polygon" in relation to the plot of a function.

 

[phinds]

Who on Earth invented this nonsense? I am shocked to see that it is part of the (GCSE) syllabus in the UK, when did that happen?

It is idiocy to confuse students by using the word "polygon" in relation to the plot of a function.

Terminology idiocy in physics (and sometimes math) is hardly limited to that one example.

EDIT: OOPS --- I though I was responding to the OP. I figure you already know this @pbuk, so now I assume that was sarcasm.

 

[pbuk]

Terminology idiocy in physics is hardly limited to that one example.

No, but to be fair to the setters of the National Curriculum in England at least they are usually quite good for Maths. Here are relevant extracts with no mention of "frequency polygons":

Key stage 3 (11-14)
construct and interpret appropriate tables, charts, and diagrams, including frequency tables, bar charts, pie charts, and pictograms for categorical data, and vertical line (or bar) charts for ungrouped and grouped numerical data
Key stage 4 (14-16) Note: the braces {} indicate content for more highly attaining pupils.
{construct and interpret diagrams for grouped discrete data and continuous data, i.e. histograms with equal and unequal class intervals and cumulative frequency graphs, and know their appropriate use}

Edit: deleted However the same cannot be said for the exam boards and the introduction of this obscure malapropism to the taught syllabus seems to be their doing, see for instance https://allaboutmaths.aqa.org.uk/application/topicheaders/guidance.php?id=10.

Edit: The exam boards seem to have come to their senses:
https://www.aqa.org.uk/subjects/mathematics/gcse/mathematics-8300/subject-content/3.6-statistics
https://qualifications.pearson.com/...cses/mathematics-2015-9-1-post-16-resits.html

It would be interesting to know if it had been examined, and if so what the result of any appeals were.

Edit: seems to be last done in November 2019, for 2 marks out of 240:

 

[pbuk]

Thanks. I'll now think of them as Frequency Polygonal Chains. I might even annoy my maths teacher by correcting her :)

You could suggest she checks that this is still part of the curriculum (see above).