# Winter 2013 MATH 307: Mathematical computing with MathematicaBranko Ćurgus

Wednesday, March 13, 2013

• In Problem 1 on Assignment 3 you need to use the Calendar package: Needs["Calendar"]. This package contains several functions related to date arithmetic: DaysBetween[], DaysPlus[], DateQ[].
An important warning: Before you use the commands from the Calendar package you must load the Calendar package. If you by mistake try to use one of the Calendar package commands without having the package loaded, you will have to quit the kernel (Evaluation→Quit Kernel→Local) before loading the package.
• The commands Fit[] and FindFit[] are essential for Problem 2 (b-3) on Assignment 3.
• The file Probabilities.nb is dealing with a problem which is similar to questions in Problem 3 on Assignment 3.
• The file PythagorasTree.nb is a "guide" for the construction of fractals in Problem 4 on Assignment 3.
• In the first part of Problem 4 on Assignment 3 you are asked to create a function that would produce iterations of the quadratic type 2 curve. In the first picture below I show the 0th iteration in blue and the 1st iteration in red. I emphasize the points that are used. You do not need to do this on your plots. In the second picture below I show the 1st iteration in blue and the 2nd iteration in red. The large picture is the fourth iteration of the quadratic type 2 curve.
• In the second part of Problem 4 on Assignment 3 you are asked to create a function that would produce iterations of the von Koch snowflake. The four pictures below show the 0th, 1st, 2nd and the 3rd iteration of the von Koch snowflake.
• In the third part of Problem 4 on Assignment 3 you are asked to create a function that would produce iterations of the Cesaro fractal which depends on angle $\alpha$. The four pictures below show the 0th, 1st, 2nd and the 3rd iteration of the Cesaro fractal with the small angle $\alpha = \pi/16$.

• Below is an animated gif file that cycles through the 1st, 2nd, 3rd, 4th, 5th and the 6th iteration of the Cesaro fractal and, within each of the iterations cycles through all the angles starting from $\pi$, proceeding towards $0$ and then back to $\pi$ in steps of $\pi/50$. The animation starts by the first iteration and cycles through angles from $\pi$ to $0$ and back to $\pi$. This is repeated for 2nd, 3rd, 4th 5th and 6th iteration. For each iteration there are 101 pictures.

• Place the cursor over the image to start the animation.

Friday, March 8, 2013

• Assignment 2 is due on Tuesday any time. Hopefully I will grade on Wednesday.
• What I did today in class is in 20130308.nb After class I added a hint how to do a general plane in the Color Cube. That involves the function Select[].

Wednesday, February 27, 2013

• The second assignment has been posted today.
• Very important tools in Mathematica are Module[] and Pure Function. I will illustrate these tools in class.
• Problem 1. This problem is quite similar to the problem solved in ExpfTanl.nb. In this notebook there are many hints on what to do in this problem.
• Problem 2. This problem is an exploration of a surprising function. You should use what you learned in Calculus, but with the power of Mathematica. This function has some surprising features that you need to discover. When you discover these features, formulate them in clear answers to my questions. Support your answers with calculations and illustrations. To explore the function use the functions D[] to find the derivative and FullSimplify[] to simplify it. To find special points you can use Solve[], Reduce[] or FindRoot[] where appropriate. However, Mathematica needs a lot of human help in this problem. It is a very good example of human-machine interaction. The notebook 20130301.nb has a lot of material relevant to this problem.
• Problem 3.
• In the first part of this problem you need to unify, as explained in the problem, three animations given below.

Place the cursor over the image to start the animation.

Place the cursor over the image to start the animation.

Place the cursor over the image to start the animation.

• In the second part you need to reproduce two pictures from Wikipidia's Cardioid page I made an animation that unifying these two pictures. You should be able to produce something like this. If not you can present one animation and one picture.

Place the cursor over the image to start the animation.

• In the third part of Problem 3 you need to produce generalized cardioids. The animations below are large. On a slow internet connection it takes a while for them to load.
• Below is the cardioid generated by a wheel with radius 1/2 rolling on a circle with radius 1.

Place the cursor over the image to start the animation.

• Below is the cardioid generated by a wheel with radius 1/3 rolling on a circle with radius 1.

Place the cursor over the image to start the animation.

• Below is the cardioid generated by a wheel with radius 2 rolling on a circle with radius 1.

Place the cursor over the image to start the animation.

• Below is the cardioid generated by a wheel with radius 3/2 rolling on a circle with radius 1.

Place the cursor over the image to start the animation.

• I will comment on Problem 4 in class.

Sunday, February 24, 2013

• I announced on Friday that Assignment 1 is due on Tuesday. Since the submission is electronic you can submit it any time on Tuesday. I will grade on Wednesday.

Thursday, February 14, 2013

• Assignment 1 has been posted today.
• There are four sources of information for this class:
• This webpage.
• My Mathematica page.
• Your Dropbox directory Dropbox\307_Files. Remember that the entire class has access to this directory. Please do not write anything in this directory and do not delete any files from there. You can copy them in your private directory. Only you and I have access to your Dropbox directory Dropbox\307_Yourlastname. This directory is exclusively for submitting your homework assignments.
• Directory Math\Curgus\307 on school's K-drive.
• Each class period I will use Mathematica for various demonstrations. I will save these files with the current date, for example today's file is 20130214.nb.
• Problem 1. Today I showed how to define `any'' funny trigonometric function using Mod[]. You can read about that in More_on_Trig.nb. However, it is possible to define the functions SqSin, SqCos, LiSin, LiCos, TrapSin, TrapCos, RoSin, RoCos in Problem 1 by using compositions of Cos, Sin, Sign, ArcCos, ArcSin and modifications of resulting periods and amplitudes. If you use functions Mod, Floor, If and similar functions you might experience problems with Plot[]. These problems are caused by the plot option Exclusions->Automatic. Changing Exclusions->Automatic to Exclusions->None might fix the problem.
• For Problem 1 you will need to carefully read the file TheBeautyOfTrigonometry.nb. Please pay attention to tricks that I introduce in that file. That should be a learning experience.
• When you adopt the content of The beauty of trigonometry to your funny Cos, Sin it is essential to pay attention to the proper domains for the variables involved. Here proper means that there should be no overlap in the parametric plots. In 3-d parametric plots overlaps can slow down plotting considerably. Your notebook should evaluate in less than 60 seconds. If it is slower, then comment out the slow parts. That is enclose the slow parts in (*    *).
• Problem 2. For some useful stuff for Problem 2 see my Mathematica page, Section: Recursively defined functions.
• You can start working on Problem 3 immediately. Essentially it uses just two functions FullSimplify[] and Sum[]. Today I demonstrated this briefly in 20130214.nb.

Tuesday, January 8, 2013

• Mathematica part of the class will start on Tuesday, February 12, 2013.
• The information sheet
• We will use
which is available in BH 215. This is the current version of this powerful computer algebra system.
• We also have
which is available on many more campus computers. This is an old, but still powerful, version of this software. These two versions are not compatible.
• To get started see my Mathematica page. Please watch the videos that are on this page before the first class.