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Using precalculus to write a TI-84 program Answered

Hello everyone,

I am in a precalculus class, and I am attempting to do a project on practical application.

The majority of students use the TI-84 for various math courses.  They are also available in the library to rent.  Unfortunately, few students take the time to actually use this wonderful tool.  I would like to create a web-type video that can be posted on the course's forums, giving a demonstration on creating simple TI-84 programs that could be used to make life a little easier.  Take a concept out of the book, and demonstrate the practical use.

Most of my hobby activity involves electronics of some sort.  I have a bad habit of explaining things far too technically.  I have difficulty explaining things in simple terms.  My goal with this project is to learn how to explain concepts in terms others can understand, and possibly to help someone else learn.

After many scrapped ideas and half written programs, I was thinking of writing a simple program that calculated the maximum number of lightbulbs that could be safely connected to a 15 Amp breaker.  I suppose it would be easy enough to allow the rating of the breaker to be a variable, but first things first.  Don't want to get too advanced before I have a clear working model. 

Can anyone suggest another role that functions play in our every day electrical/electronic life?

Many thanks.


So very true and unfortunate that students are rarely taught about a tool that many use daily. Learning how to efficiently operate calculator seems give give a definite advantage over those who don't. That was the major influence for wanting to do this.

What about demonstrating charge/discharge for capacitors? This could be defined as an exponential function in the form of
f(x) = (100.3140741)(0.6056796398)^x
where is restricted to [0,5] (due to there being only 5 charging cycles)

Obviously I have not completely worked through this, but that's the general idea. Capacitors may go beyond some of the students' understanding. But others may understand the concept. Some may become more interested. Either in capacitors or in the capability of practical usage of a TI84.

Thank you for all the ideas. I really wanted to stay with electronics as the basis, but if this does not work out, I may use some of these ideas.

Make sure whatever you choose to do (I'm not sure the lightbulbs to a breaker thing is the best idea just because most students don't care about that sort of thing and some of them probably don't even know what a breaker is or what it does. You'll spend just as much time trying to explain breakers and wattage as you will programming the calc. I think it's great but I just think it's the wrong audience.) relates back to the course in some way by using one or more of the formulas or concepts being covered.

[tangent] Man, talking about programming TI's takes me back. I wrote a ton of programs in in high school/college to handle the formals we used all the time, like the quadratic formulas. Although I probably spent more time drawing and programming animations. Drawing all the frames using the graphing tools wasted more class time then I'd like to admit. [/tangent]

Back when i was in high school teachers would teach us how to write a basic program into the Ti-81 and Ti-82 to draw out a sin wave or demonstrate some other mathematical formula. This was about the time the Ti-85 came along and people learned to hack the calc and program it in ASM. Most of the basic programs i did where games but some where to have formulas available so i wouldn't have to memorize them for the test.

I'm surprised teachers don't cover more of the calcs functions and how to use them. At the school i went to they had special teacher versions of the TI-82 that connected to a screen that went on an overhead projector so they could demonstrate the calc and its functions.

Some obvious examples, all of which can be implemented algorithmically:

  • compound interest (which also brings in recursive functions)
  • gas mileage, especially instantaneous vs. average
  • material optimization (multivariate analysis -- given unit prices for bolts, wood, etc., how large a room can you build for X dollars, or what budget do you need for a Y-sized room/building)
  • surface/volume relationships, or, "why should infants be bundled up?"