|Re: common math errors|
Message #5 Posted by Palmer O. Hanson, Jr. on 27 Sept 2006, 9:19 p.m.,
in response to message #4 by Palmer O. Hanson, Jr
The thread discussiing the -3^2 problem is "TI-84 Plus really that clumsy?" near the top of Archive 16:
Early in the thread the -2^2 problem was introduced:
"Re: TI84 plus really that clumsy??
Message #3 Posted by John Smitherman on 4 Sept 2006, 3:11 p.m.,
in response to message #1 by Hal
Hi Hal. Also, tell your son to be careful with the TI-8x series as it interprets -2^2 as -(2^2) instead of (-2)^2.
Re: TI84 plus really that clumsy??
Message #4 Posted by Valentin Albillo on 4 Sept 2006, 3:22 p.m.,
in response to message #3 by John Smitherman
" Also, tell your son to be careful with the TI-8x series as it interprets -2^2 as -(2^2) [...]
As it should. That's the correct way of interpreting -2^2, and the HP-71B does exactly the same, returning -4. If you want (-2)^2, you should write it that way, parentheses and all.
If in doubt, check any math books or articles and look for terms such as -a2 , you'll easily find them aplenty. Do you really think the author actually intends you, the reader, to interpret that term as (-a)2 instead ? Unary minus has lower precedence than exponentiation in standard math writing.
Best regard from V."
And the thread goes on and on from there explaining how a user can get different answers depending on how the problem is entered into different machines. What I think that all really says is that RPN really isn't the solution to reducing math errors by students. Neither is AOS, EOS, RPL, BASIC, FORTRAN, or whatever. First, the student has to know and understand the mathematics conventions. Then, the student has to understand the conventions for the machine he is using. Then, he has to be careful.