# Calculus I

[catlist name=Calculus numberposts=50 excerpt=no order=asc]

# Equations between WordPress, Open Office and LaTeX

Equations in WordPress

These are the steps to create LaTeX equations on non-WordPress.com blogs.

1. Install and activate Jetpack.
2. Connect your self-hosted WordPress blog with your WordPress.com account by going to “Settings” of the Jetpack plugin.
3. I prefer to use Open Office Writer to type equations. To turn these formulas into LaTeX format, I downloaded and installed Writer 2 Latex. (To install the plugin, I double-clicked two different .oxt files: writer2latex.oxt and writer4latex.oxt. I’m not sure what the difference is, but it seems to work.)
4. Once you have Writer 2 Latex installed, a “LaTeX” menu item should appear. You can click that and a LaTeX document will appear in the same directory as the OOWriter document you’re working in.
5. You can then open the .tex file with, as I do, Notepad++ or another text editor.
6. Alternatively, you can go to a site like this one.

# How do they calculate what your monthly auto loan payment will be?

So, I recently bought a new vehicle and was wondering how my monthly payments were figured out. After digging around a bit, I found this site where a high school teacher has posted the formula as an exercise for her students. Not only that, but I stumbled across this other website where I could find simple solutions to the most of my financial woes.

Well, I thought I would share this gem in case anybody else is interested.

$\frac{P(\frac{i}{12})}{(1-(1+\frac{i}{12})^{-n})}$

You can go to this site and the Almighty Internet will give you the same answer.

Alternatively, you can download this document I made in Open Office Calc (free) and see, with your own eyes, what’s going on.

I would love to know, if anyone ever reads this, how the initial finance charge is decided. I thought about it, fruitlessly, until my brain hurt.

Here is the problem:
You have a principal amount of $4049.00. Your finance charge is calculated to be$538.12. Your interest rate is 8.29%. What formula was used to arrive at the value \$538.12?

# Exponential Growth/Decay

The mass of a radioactive substance follows an exponential decay model, with a decay rate of 5% per day. Find the half-life of this substance (that is, the time it takes for one-half the original amount in a given sample of this substance to decay).

Do not round any intermediate computations, and round your answer to the nearest hundredth.

Answer in PDF (read only).
Answer in ODT (read/write).

# The I-Pen and Paint.NET for Math

For anybody looking to make writing out equations on your computer easier, I have two recommendations:

First is the I-Pen (pictured above). It’s plug and play, but I think I had to install software either for my mouse or for the I-Pen itself to make the two device pointers move at two different speeds (you will probably want the I-Pen to move more slowly for greater accuracy).

Second, I have made this blank worksheet for working out problems in Paint.NET. I was using the version of Paint that comes with Windows 7 and it’s quite nice, but I wanted something with greater functionality that would work on my netbook (running Windows XP) as well. So, Paint.NET works well.

The only problem was that I don’t want to have to mess with layers and selecting a canvass size I like every time I need to work through one or a whole slew of equations. So, the above-referenced “blank worksheet” has proven useful so far. I open it once and then each time I want to begin a new equation, I press and hold the “Ctrl” key on the keyboard and tap the “A” key (to select all) and then press the “Delete” key. Voila. Blank math canvass in approximately two seconds.

One issue with this approach is the way that Paint.NET handles layers. In order for my approach to work as intended, the layer settings window must look like this:

However, quite annoyingly, when you close and reopen this saved document, the layer settings window looks like this:

So, it must be changed back each time to allow trouble-free math drawing.

# Finding Reciprocal Functions SEC, CSC, COT on TI-30XA

First, you may want to refresh your memory of the regular trig functions:

Now, let’s find $\csc \frac{5\pi }{4}$.
If we look it up on WolframAlpha, we find that it equals $-\sqrt{2}$, or, roughly, $-1.4142$.

To get this answer on the TI-30XA, first remember that $\csc$ is equal to $\frac{1}{\sin }$.

So, what we’re looking for could be expressed as $\frac{1}{\sin \frac{5\pi }{4}}$. Once we know this, we can type $5\cdot \pi$ into the TI-30XA.

This gives us ~15.7. (Make sure you’re in radian mode. If not, press the DRG button — located by the 2nd button, upper-left — until you see RAD appear in small letters on the screen.)

Now, we can divide 15.7 by 4. This gives us 3.925. If we take the $\sin$ of this (by pressing the “sin” button while 3.925 is displayed), we get $-0.7$. IF we divide 1 by $-0.7$, we get $-1.43$. As you can see, this is close to the correct value. You can get a more exact value by using the STO function on the calculator. [Press “STO” while a number is displayed on screen and then the number “1” on the keypad. Press the clear button (ON/C). Now, press RCL and the number “1” on the keypad. Your saved value should appear.]

# Statistics Miscellanea

Formulae Quizzes (use the learn feature): one, two

T test
t Table
t value calculator
reporting results of repeated-measures t test example: Changing the background color from white to red increased the attractiveness rating of the woman in the photograph by an average of M = 3.00 points with SD = 1.50. The treatment effect was statistically significant, t(8) = 6.00, p < .01, r2 = 0.818.

Chi-square
Chi-square Critical Values