Need help for some HP Prime calculus/functions

[Devil69]

(12-22-2019 06:09 PM)Nigel (UK) Wrote:  

(12-21-2019 01:39 AM)Devil69 Wrote:  ...

Also nobody can help me with trig inequations?

Thanks

I'll have a go!

If I try to solve (for example) \(\sin(x)>\frac12\) in CAS mode on the Prime, I do indeed get the error message given in your first post. But if I enter

Code:

assume(x>=-pi && x<pi)

first, I get the correct answer -
\( \left\{x>{\pi\over 6}\;{\rm and}\; x<{5\pi\over 6}\right\}\).

It seems that when you are solving a trig inequality you must specify the range in which solutions must lie. You can't leave this unspecified, as you can for an equation. There is probably some good reason for this which I can't think of at the moment!

Look up the commands assume, about, and purge in the manual or in the Help system for more information.

Hope this helps!

Nigel (UK)

Hi Nigel thank you very much I followed your instructions and it finally worked!
I think HP should add the variable "k" for trig (in)equations in their future update to do these operations without assume() function so that the answer looks like this:
x>π/6+2kπ and x<5π/6+2kπ, k∈ℤ