|Re: HP 50g - Good tutorials|
Message #3 Posted by Crawl on 21 Sept 2011, 9:53 a.m.,
in response to message #1 by François Vanzeveren
Vaguely related, I sometimes save formulas to my HP50g's SD card. But sometimes it's not so easy to do. Example, let's say I want to save a matrix formula, like
[a b] [x] = [m]
[c d] [y] [n]
or even worse,
[x] = ([a b])^-1 [m]
[y] [c d] [n]
How do you do that? If you enter this stuff on the stack, it's just evaluated immediately.
Then I though, Aha! In algebraic mode, after you enter an expression, the original expression is displayed, then the evaluated version! I can copy that original expression, go back to RPN mode, paste it, and save it!
By the way, it turns out that if you enter matrix equations like that, you'll probably get an error (it probably tries to evaluate the equation to a Boolean value, but it's indeterminate since it's symbolic). But it doesn't matter if the second line is an error; the first, which is what I want, is correct.
So there's a use for algebraic mode after all!
It turns out that when you save expressions that way, they're considered to be "tags". There's probably a way to enter them as tags directly in RPN mode, but for now this might be easier for me.
This is why I wish this calculator had a product (capital Pi) function. Yes, in terms of computation, you can do it with the Sum function and logs. But if you want to save a formula so it would look nice, you'd want Product.