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When y= a constant, how do you find the interval of definition?

  1. Jan 27, 2013 #1
    I used the linear equation method to solve a D.E. and got y=3/4 at the end. I'm asked to find the interval of definition but I don't know how to do that when Y is just a constant :/
  2. jcsd
  3. Jan 27, 2013 #2
    If your solution is y=c then dy/dt must have been 0.
    Unless it was specified that dy/dt=0 on some particular interval, then your solution should be valid for all t.
  4. Jan 27, 2013 #3
    So the interval of definition would be (-∞,∞)?

    I just don't get how a function can have a domain when it's just a constant...
  5. Jan 27, 2013 #4


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    Homework Helper

    If your function is y(t) = 3/4, it means that for any t you give the function as an input, the function returns the value 3/4. So, the domain is whatever range of values of t you are allowed to put into your function. It doesn't matter that your function happens to return a constant in this case.
  6. Jan 27, 2013 #5
  7. Jan 28, 2013 #6


    Staff: Mentor

    Every function has a domain.
    I wouldn't use the word "range" when you're talking about the domain, because of confusing the issue with the function's range.
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