Re: RPN and students Message #5 Posted by Palmer O. Hanson, Jr. on 14 Dec 2010, 11:01 p.m., in response to message #4 by Chuck
Quote:
The one I use is:
Solve 300=2.45 e^(.025x) +35for x.
Using RPN you can solve it without writing anything down (just perform the inverse operations):
300 ENTER
35 
2.45 /
ln
.025 /
On an algebraic input calculator, you almost have to solve it on paper first (or do some mental gymnastics) in order to see exactly how to type it in:
ln((30035)/2.45)/.025 =
which just looks atrocious.
If the user of a TI83+ wants to solve by generating the equation for x he does NOT have to derive the equation by using pencil and paper and then enter the derived equation into his machine. Rather, he uses the display as a scratchpad and uses the cursor keys and the insert function to generate the derived equation in the following manner
Place (30035)/2.45 in the display
Realize he has to insert the ln function at the front. Slew to the left margin, press 2nd INS, press ln and see ln ( inserted at the front of the equation.
Slew to the end of the entered equation and press ) / .025 and see the derived equation in the display as
ln((300350/2.45)/.025
and press ENTER to solve. It seem to me that the solution for x isn't atrocious. It is just what it is.
The user of the TI83+ does NOT have to solve by entering the equation in that manner. Rather, he can solve the problem as follows::
300  35 ENTER
/ 2.45 ENTER
LN 2nd ANS ENTER
/ .025 ENTER
which yields the same intermediate displays as would be received with a typical RPN machine. The same sequence will work on any of the TI graphic machines. A similar sequence will work in algebraic mode on the HP35s.
