# Diff equation last step of the solution

1. Jul 11, 2009

### electron2

after solving a long diff question i got

0.5*u(t+1)-0.5*u(t-1)

where u(t) is a step function for t>=0 its 1
and t<0 its 0

my expression looks pretty finite to me

how to continue??

2. Jul 11, 2009

### Hootenanny

Staff Emeritus
I don't understand the question. Does your expression form part of an equation? What is the end goal?

3. Jul 11, 2009

### electron2

my expression is the final solution
but i was told that it cam be developed further more

how??

4. Jul 11, 2009

### Hootenanny

Staff Emeritus
You're expression cannot be the final solution since it is not an equation! What is on the left hand side of the equality sign?

However, linear combinations of heaviside (step) functions can often be written in terms of the rectangular function.

5. Jul 11, 2009

### electron2

believe me there is a left side
its some intergral
and its not important

how to write it in terms of the rectangular function?

6. Jul 11, 2009

### Hootenanny

Staff Emeritus
Okay, if you say so.
Try googling rectangle function.

7. Jul 11, 2009

### electron2

8. Jul 11, 2009

### Hootenanny

Staff Emeritus
Well you obviously didn't look hard enough since the answer is virtually given in the second equation!
I'm here to help you with your work, but I'm not simply going to give you the answer.

9. Jul 11, 2009

### electron2

ok so look at it as if
i asked to solve the whole question
and i showed the solution till some point
and i need to finish it

by saying
"I'm here to help you with your work, but I'm not simply going to give you the answer."

you are not helping at all
you could give a hint
or a article

but you didnt

10. Jul 11, 2009

### Hootenanny

Staff Emeritus
I did give you a hint in post #6, which lead you to an article. I then gave you another hint in post #8, the answer is given there in the second formula on the wiki page!

11. Jul 11, 2009

### electron2

the formula is with (t-0.5)

and i have t-1

how to suit it with my expression

12. Jul 11, 2009

### Hootenanny

Staff Emeritus
Let's have a look at the expression,

And compare with your expression,

$$f\left(t\right) = \frac{1}{2}\left[u\left(t+1\right)-u\left(t-1\right)\right]$$

So, what do you have to set tau to, in order to make wiki's expression the same as yours?

Last edited: Jul 11, 2009
13. Jul 11, 2009

### electron2

so tao=2

so its f(t)= [rect(t/2)]/2

correct?

14. Jul 11, 2009

### Hootenanny

Staff Emeritus
Indeed it is

15. Jul 11, 2009

### electron2

thanks

Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook