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I How to invert unit step function?

  1. Jan 13, 2017 #1
    I am trying to find out how to reverse the unit step function. The closest I could find is this sentence, which is more like a definition?

    "if we want to reverse the unit step function, we can flip it around the y axis as such: u(-t). With a little bit of manipulation, we can come to an important result:

    I completly get how 1-U(t) would be positive 1 until t=0 and then it becomes 0... But how does t change to -t?
  2. jcsd
  3. Jan 13, 2017 #2


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    Staff: Mentor

    The equation there is an identity. It can also be written as u(t)+u(-t)=1.

    It does not change the function, but it tells you how you can change the function: u(-t) is the reversed function (by definition), but instead of this you can also use 1-u(t) because those two things are the same.
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