I had an Algebra2 / Trig teacher who handed out a 'how to' sheet on Side Angle Side and Angle Side Angle trig work (finding the sides and angels of a triangle with only 2 sides and their angle or one side with two angels)
By the end of that class period I'd coded the thing into my TI-83 and showed it to her.
She let me use the program on tests because I showed my understanding of the problem well enough to translate it to TI-Basic.
The TI-83 came out in time for my senior year of high school, but I took Algebra 2 in my junior year so got a TI-82. There wasn't much difference between the
original TI-83 of '96 and the TI-82, although the later
TI-83 silver or TI-83+ had more memory (which was either extremely useful if you loaded the calculator with games and math programs or useless if your school made you reset the calculator before tests to prevent this kind of "cheating").
I used the program in a similar way to do things like that, or in Algebra and Pr-calculus to do things like complete the square. The teachers were ok, since it just gives you the answer, on the tests and homework you have to show your work to get full credit.
Then I pissed them off because I wrote a program to show the work and I just had to copy it off the screen.
What really pissed them off was me selling the program to other students before a test using the TI-GraphLink so they just had to copy off my program. I originally tried doing it as soon as the program became available to help with homework, but ran into piracy problems. They saw no reason why each should pay $5, why not just all chip in, give my $5 and then spread it around themselves.
The teachers told me that they didn't have a problem with me writing the programs and using them myself because it shows I understood the material well enough to code it. They had a problem with me selling it to other students who might not understand how to do something like complete the square and can now do it on a test, and show the work as well.
Complete the square was not the only such program I did that to, it's just that one particular program sticks out because it's the one they all yelled at me for selling and all the rest kinda blur together as it's been 25 years.