When to use equal to or equivalent to?

  1. Dec 4, 2013 #1
    When is it appropriate to use [itex]\equiv[/itex] as opposed to =?
  2. jcsd
  3. Dec 4, 2013 #2


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    Gold Member

    well, here are a couple of examples, although I don't know that it would ever be wrong to use = when you mean equivalent.

    y = ax + b [this is an "assignment" which is typical for "="]

    a + b == b + a [this is not an assignment but a statement of equivalence]
  4. Dec 4, 2013 #3


    Staff: Mentor

    Use ##\equiv## for equations that are identically true, such as (x + 1)2 ##\equiv## x2 + 2x + 1 and sin2(x) + cos2(x) ##\equiv## 1. Each of these equations is true for any real x.

    Use = for equations that are conditionally true, such as 2x + 1 = 5. This equation is true only for x = 2; i.e., only under certain conditions.
  5. Dec 4, 2013 #4
    Oh ok. Thanks Mark & phinds! That really cleared it up!
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