# what are these

Discussion in 'Homework Help' started by Asad ahmed1, Feb 10, 2016.

1. ### Asad ahmed1 Thread Starter Member

Feb 10, 2016
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Its my exams next week I took a look at the previous paper and i found this section in it can anyone please tell me what i have to study in order to complete this section please help me.

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2. ### kubeek AAC Fanatic!

Sep 20, 2005
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A schoool of some sort would definitely help.

3. ### Asad ahmed1 Thread Starter Member

Feb 10, 2016
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I asked my professor about this but he was not willing to tell me anything and in class he doesn't tell us anything at all

4. ### kubeek AAC Fanatic!

Sep 20, 2005
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Fisrst is an exponential equation, the second two are from trigonometry, both basic high school math.

5. ### Asad ahmed1 Thread Starter Member

Feb 10, 2016
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so what would be the time constant of this exponential equation

6. ### kubeek AAC Fanatic!

Sep 20, 2005
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This being a homework forum, try showing some effort on your side. You need to find out what that exponential equation is and then solve it.

7. ### Asad ahmed1 Thread Starter Member

Feb 10, 2016
68
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it is not a homework problem i dont know anything about it.so tell me what is it so i can study about it and be prepared for the finals.i searched exponential equation but no luck

8. ### kubeek AAC Fanatic!

Sep 20, 2005
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Edit: deleted irrelevant reply

Last edited: Feb 10, 2016
9. ### Asad ahmed1 Thread Starter Member

Feb 10, 2016
68
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so how would i be able to find the time constant and yeh 2 other questions what i have to study which topic what i would write in search engines to find this type of things.

10. ### WBahn Moderator

Mar 31, 2012
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It doesn't matter whether it is an actual, explicit homework problem. In this forum YOU are expected to at least make an honest attempt to solve the problem. We will not spoon feed you solutions just because you claim that it is not an assigned problem.

If you really have absolutely no idea what an exponential equation is or what a time constant is or how they relate to each other, then you need to drop this class and retake the prerequisite course(s).

Mar 31, 2012
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Huh???

12. ### WBahn Moderator

Mar 31, 2012
18,087
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How about trig identities? Step functions?

13. ### Asad ahmed1 Thread Starter Member

Feb 10, 2016
68
0
ok ill tell you what i know so far we get exponential decay when capacitor or inductor is discharging e^-t/tao in this question they have given us the decay of 70.7 percent when t=0 and we have to find it when its in t=5 second so do can i do this when e^-0tao=70.7 and now e^-5/tao
thats i know so far .

14. ### WBahn Moderator

Mar 31, 2012
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Read the question more carefully.

15. ### Asad ahmed1 Thread Starter Member

Feb 10, 2016
68
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find the time constant which decay to 70.7 we have to find tao in 5 second does it means e^-5/tao=70.7 am i close ?

16. ### WBahn Moderator

Mar 31, 2012
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(Find the time constant) (of an exponential function) (which decays to 70.7% (of its initial value at t = 0) in 5 msec).

17. ### Asad ahmed1 Thread Starter Member

Feb 10, 2016
68
0
v=e^-1 =0368 means 36.8 percent
so i need a value of tao to make 70.7 percent

Last edited: Feb 10, 2016
18. ### kubeek AAC Fanatic!

Sep 20, 2005
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sorry that was meant to go to another thread.
And to be true, I think this thread was somewhere else than homeworks when I first replied to it.

19. ### WBahn Moderator

Mar 31, 2012
18,087
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Figured it was something like that -- but had to jerk your chain a bit.

Very possible.

20. ### WBahn Moderator

Mar 31, 2012
18,087
4,917
First things first.

You have an exponentially decaying function.

So start with an exponentially decaying function.

y(t) = what?