## September 12, 2006

### Scribe Post: Day 3

Hi everybody, my name is Crystal and I will be your scribe for today. :D

During class we discussed more about blogging. This years AP Calculus class has gotten off to a great start. Mr. K. talked about Scribe Post Hall of Fame (http://thescribepost.pbwiki.com). Which is a page of the best scribe posts throughout the entire history of this website. I believe the Applied class last year was in it 12 times in a row. Our class can surely accomplish that, no problem. :) Well, just remember to post up comments on how the posts should be inducted into the Hall of Fame. The students should judge; "It looks good, but did I learn?"

Okay down to business, the following questions are the problems we solved today:
#1) If f(x)=√(x2+8)

a) Find domain of f(x)
First let's see what we basically know: Remember you can not square root negative numbers! Aslo, when graphing f(x) it is a parabola opening upwards. So let us check if this function has x-intercepts:
x2+8x=0
x(x+8)=0
x=0, -8
Therefore D=(-∞,-8]U[0,∞)

b) Write a formula for the function whose graph is the reflection of f(x) across the y-axis.
So only the x-coordinates change.
f(-x)=√((-x)2+8(-x))
f(-x)=√(x2-8x)

c) Write a formula for the function obtained by shifting f(x) 3 units right, flipping the graph over the x-axis, and then shifting it up 4 units.
This question contains three transformations:
Horizontal Shift: f(x-3)=√((x-3)2+8(x-3))
Reflection of y-axis: f(x-3)=-√((x-3)2+8(x-3))
Vertical Shift: f(x-3)+4= - √((x-3)2+8(x-3))+4

#2) "In Winnipeg at 5:00, headed for Gimli, a distance of 60 miles. Due to an accident on the highway, traffic was creeping along for the first hour and a half. By 6:30 we were only 20 minutes from Gimli. After that we were able to speed up gradually and finally reached Gimli at 7:30."

a) Draw a possible graph to represent the distance in miles from Winnipeg, as a function of time, in hours since 5:00.

b) Explain the important features of your graph, including commonts on concavity.
At the beginnig the car travels at a constant speed while in traffic, the car then speeds up as it is freed from traffic, then it slows down as it comes closer to reaching it's destination.
Near the end is where concave downward happens; it bends down.

We also completed the question we started on September 9.
We found out that f(x) is an exponential function.

Here are the instructions for solving this problem on your graphic calculator:

1. STAT, Edit, Now fill in the table. *Make sure to ClrAllLists*
2. 2nd STAT PLOT, Plot1 on, on, scatter plot
3. ZOOM 9 (ZoomStat)2nd QUIT, STAT CALC 0, ExpReg, L1, L2, Y1, ENTER
4. If r2 or r (corolation of coefficient) doesn't show up press:2nd 0 (CATALOG), DiagnosticOn, ENTER, then go back

Therefore f(x) is an exponential function.

HOMEWORK: 1.3 odd numbers and question 2

This was a bit difficult, since I'm computer-illeterate. But I guess I did okay, did my best. Alright who shall I choose... hmmmm.... are next scriber is LINGER! 8D

linger said...

Crystal, I really enjoyed reading your scribe even if by the end of it I found my name.. haha. Anyway, I like the way you used the colours; it not only looks pretty, the way it was used helped me understand better. Also thanks for putting the link down for the Scribe Post Hall of Fame, I misplaced where I wrote it. I'd like to add that when we were working on the last question and trying to decide whether g(x) was a line or the other type of function (I forgot which one) Mr. K said something about deciding what type of function it is by not only what the calculator tells you [by what r tells you], but also by comparing the graphs, and seeing which one makes sense and fits better. He said that you have to hunt around in order to make a good decision. Anyway, thanks again =)

tcnashlynn said...

Hey Crystal! I know exactly what you mean about being computer-illiterate!! haha I'm still trying to find my way around this blogging thing. Well anyway, your scribe was very helpful! It was easy to understand. I am a bit confused about the calculator thing, but your explanation helped ALOT. I was listening in class but then I forgot MOST of what I learned. The class scribe really helps!

lindsay said...

your scribe was very helpful, crystal! i liked the way you used colours...i love colours! i understand the lesson better now. in class, i'm lost most of the time so your scribe made me worry less about not understanding things. =)

be happy!

Jann said...

Hi Crystal,
Your scrib is nicely done. Dont worry about the pics, its still A-OK. Thanks for citing some of the details i missed. It really helped me.

Lani said...

Hi Crystal,

Linger has really identified that your use of color helped understanding!

It appears that you already see the value of the scribes to deepen your understanding! That's great. Crystal, I'm sure you are absolutely correct; your class can surely accomplish many Hall of Fame Scribes.

I'm not sure what kind of problems you were having with graphics. Pasting won't work. When you are in Paint, save your graphs as jpeg or gif. Would these two links be of help?
How do I post pictures and

I'm thinking other students around the globe in calculus may want to learn from your scribes. Do you think it would be helpful to put the major topic of your scribe in the title so they can more easily find the information they seek?

Best,
Lani

M-A-R-K said...

=T exactly what lani said, you should save your grapsh and drawing as jpeg. The files are bigger than 1000 kb, blogger won't allow you to upload a file that big =p. JPEG will make the file smaller by like 1000% (50-150 kb)

crystal said...

Thanks lani and m-a-r-k for both of your help on the pictures!! I thought I looked through all of the Helps about graphics but I missed a few. Those sites helped a lot lani. :) Also I found out my file was too big. It was saved on jpeg and my graph was small, but it was just on a large paper, you know how Paint is. Thanks again for both of your tips :D