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After a class-wide tangent about the nature of...

I haven't found the exact meaning of this word in dictionaries in this particular sentence

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  • Welcome to EL&U. What meanings did you find ? I would be surprised myself if the word 'classroom' can be attached to the word 'tangent', but stranger things have happened.
    – Nigel J
    Commented Mar 20, 2018 at 11:24
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    Look at an image of a mathematical tangent. Rather than following the perimeter of the circle around, the tangent line shoots off on its own.
    – Hot Licks
    Commented Mar 20, 2018 at 11:59

2 Answers 2

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In mathematical terms, a tangent is a line that meets a circle at precisely one point, before continuing into the distance. So it doesn't cross the circumference, but only grazes it.

So to "go off on a tangent" is a figure of speech that means to get distracted or sidetracked from the main topic and spend on something that is only loosely related to the matter at hand.

So if you started out talking about one thing, then got reminded of something, so you ended up talking about that, which reminded you of something else, and then something else...
You went off on a tangent.

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  • Actually, mathematically, a curve is a tangent to another curve roughly speaking if they share exactly one point. (In this context, "a line" counts as "a curve"). "Roughly speaking", because I don't know whether mathematicians consider curves with sharp points (eg y = abs(x) + abs(sin(x))) as being tangential to another curve (eg y = 0) that they touch at the sharp point (in this example [0,0]) Commented Mar 20, 2018 at 13:14
  • If you tie an object to a string and spin it around, so it goes in a circle, and then cut the string. It will fly of at a tangent. Along the line described in this answer. Commented Mar 20, 2018 at 13:44
  • @user288754 remember to mark this response as accepted if it answered your question. :) Commented Mar 20, 2018 at 15:00
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There's not much info in your question but I'll give a try.

In mathematics a tangent is a curve or line that lies on or touches another line or curve. It comes from the Latin "tangere" which means to touch.

Here is an example of a tangent:

enter image description here

It can also mean the tangent function, but don't worry about that because I think your question is about the non-mathematical meaning.

In ordinary English a tangent is like a digression. Let's just say you're talking about a certain topic, and you make some brief side remarks about another topic, that would be "going off on a tangent" / digressing / changing subject.

  1. on a tangent at a tangent on a completely different or divergent course, esp of thought: to go off at a tangent.
    source: Collins Dictionary

I don't have etymological evidence to back me up but I strongly believe that this usage has come from the metaphor of a line diverting from another course, as seen in maths.

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  • "A completely different line of thought or action", I'd assume it meant "going off topic", but I'm not sure
    – user288754
    Commented Mar 20, 2018 at 11:27

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