HP Prime Trig Simplify

[drake2...@gmail.com]

Is there a way to program the HP Prime to understand things like "[1-COS^2(x)/COS^2(x)]" is equal to "TAN(x)"? The HP Prime seems to struggle when it comes to trig identities.

[Irl]

On Sunday, November 4, 2018 at 4:58:06 PM UTC-5, drake2...@gmail.com wrote:
> Is there a way to program the HP Prime to understand things like "[1-COS^2(x)/COS^2(x)]" is equal to "TAN(x)"? The HP Prime seems to struggle when it comes to trig identities.

Your specific example is problematic. Presumably what you meant was something like
[1-COS^2(x)]/COS^2(x)
not
[1-COS^2(x)/COS^2(x)]
which, by the way is equal to TAN^2(x), not TAN(x). If instead you meant
SQRT([1-COS^2(x)]/COS^2(x))
then that is either TAN(x) or -TAN(x). I don't have a Prime but if you put in the correct formulas does it work more as you expect?

[drake2...@gmail.com]

Yes, what that's what I meant. But no, it still just gives back my entry of [COS^2(x)-1]/COS^2(x). Is this a problem with other HP calcs, or is the Prime the only one with a CAS or what? I know the TI nSpire CAS's do fine with trig identities.

[d...@ddoherty.net]

On Monday, November 5, 2018 at 8:32:29 AM UTC-6, drake2...@gmail.com wrote:
> Yes, what that's what I meant. But no, it still just gives back my entry of [COS^2(x)-1]/COS^2(x). Is this a problem with other HP calcs, or is the Prime the only one with a CAS or what? I know the TI nSpire CAS's do fine with trig identities.

HP 50-g returns TAN^2(x) when TRIGTAN is applied to the formula.

[drake2...@gmail.com]

So it does at least have that functionality. That's a good step in the right direction I suppose. Would there be (any) way for me to get the calculator to do something like that automatically? That's obviously the simplest answer. I don't think I should have to run the answer through another function. Plus, if I'm doing a rather complex CAS computation with trig, I don't want to have to reverse engineer what the calculator did just so I can simplify using trig identities. Is there a way to rewrite/expand how the calculator handles simplifying trig expressions to accomplish this?

[Bruce Horrocks]

On 05/11/2018 14:32, drake2...@gmail.com wrote:
> Yes, what that's what I meant. But no, it still just gives back my entry of [COS^2(x)-1]/COS^2(x). Is this a problem with other HP calcs, or is the Prime the only one with a CAS or what? I know the TI nSpire CAS's do fine with trig identities.
>

Using the PC emulator, freshly reset, in CAS mode, I get:

(cos(x)^2-1)/cos(x)^2 => (cos(x)^2-1)/cos(x)^2
trigtan(ans) => -tan(x)^2

--
Bruce Horrocks
Surrey
England
(bruce at scorecrow dot com)