# Homework Help: Plotting singularity functions

1. Sep 15, 2014

### princejan7

1. The problem statement, all variables and given/known data

Can someone explain how the expression for V(x) is plotted?

2. Relevant equations

3. The attempt at a solution
I understand the plots for the dotted lines but not how they got the actual plot for V(x)

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2. Sep 15, 2014

### CWatters

It's been awhile since I did this but I think you just sum the dotted curves region by region.. I'll do the region shown in green on my copy of your diagram..

At the start of the region you have..

+8 from (a)
-32 from (b)
+0 from (c)
+40 from (d)
= +16

Then at the end/right you have

+8 from (a)
-48 from (b)
+16 from (c)
+ 40 from (d)
= +16

So in that region the result is a horizontal line at +16.

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3. Sep 18, 2014

### princejan7

thanks, I have another question:

at x=6, I'm supposed to be getting V(x)=0 but summing the dotted curves, I get

(23/4) -3(6) +3(3) + (1/6)(6^2) - (1/6)(3^2) + 2(3) + (7/4)
=9

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4. Sep 19, 2014

### BvU

Does that mean you think the exercise has been answered properly ? I think I see an ans (2) on the picture, but I have no idea what the question is!
By the way: read the guidelines and fill in the template. Include an explanation of what <> [ ] and the superscripts 0 and 1 mean. That way others can read what this is about!

You then post another question: "I'm supposed to be getting V(x)=0". Well, I get that too, but just by deciphering the funny code these authors use to indicate intervals and to describe V. Not by dallying around with 23/4 and all kinds of other fractions. What is this ? Where do you get these dashed lines from? What do they represent ?