GEOMETRY application - a problem
03-25-2020, 10:47 PM
Post: #1
 Jan 11 Junior Member Posts: 25 Joined: Mar 2020
GEOMETRY application - a problem
I wanted to report problems in the GEOMETRY application. The program does not find all intersection points of two functions y = f (x). For example: y = sin (x) and y = cos (x). The inter (GA, GB) or similar single_inter command finds only 2 intersection points and one foreign intersection (see this in the attached screenshot). However, when I introduced the restriction, x> 0 AND x <18, I again received only one real solution and one foreign one. However, I noticed a very interesting thing. When I entered the CAS application and entered coordinates (GC), I received a beautiful list of all solutions. Awesome. It follows that CAS calculates well the solutions of the system of equations sin (x) = cos (x). However, the PLOT graphic window does not mark these intersection points.
In the second example, there are functions y = abs (x) -5 and y = x ^ 2-5. And here is also a problem. There are 3 solutions for this system of equations. The calculator graphically found only two. In the third example, we have y = (1/2) ^ x and y = -x ^ 2 +3. There are 2 points of intersection. The calculator graphically showed only one intersection. And the last example. The functions y = LOG (x) and y = x ^ 2-5. There are two solutions. In the PLOT window we see one true and one foreign solution. However, CAS did not provide all the solutions in the last three examples. He showed similar solutions as the PLOT graphic window. And this is a problem and a mistake.
These are serious errors that must be urgently removed. And another important detail to this topic. I used to solve all these graphical systems of equations using Firmware Version 2013 11 25 Rew. 5447.
There was no problem. Everything has been solved correctly. I can not understand it.

03-26-2020, 07:53 AM
Post: #2
 parisse Senior Member Posts: 1,187 Joined: Dec 2013
RE: GEOMETRY application - a problem
I just checked, I get correct answers with the latest CAS.
You have recently reported some problems related to the CAS with screenshots. Could you please give a commandline instead?
Like solve(abs(x)-5=x^2-5)
That way I'm sure I have the correct command because I can copy/paste. And it's faster for me. Thanks.
03-26-2020, 08:21 AM
Post: #3
 Jan 11 Junior Member Posts: 25 Joined: Mar 2020
RE: GEOMETRY application - a problem
Parisse, I checked the solution of this equation in my HP PRIME G1 calculator and in a virtual calculator. Graphically and in CAS, I have only two solutions. I miss the solution (0, -5). I have installed in my HP PRIME G1, Firmware 2.1.14425 (2020 01 16). I am using the inter command in the Geometry Symbolic View window. And in CAS, the "coordinates" command. And what Firmware do you have that you have the right solutions
03-26-2020, 08:40 AM
Post: #4
 parisse Senior Member Posts: 1,187 Joined: Dec 2013
RE: GEOMETRY application - a problem
As I said, I checked with my latest development version, and also with the public Mac emulator version 2018/07/06 (I can not check with the latest public Mac emulator, it is not compatible with my OS X version).
I did not check with the geometry app, but with the corresponding CAS commands
solve(abs(x)-5=x^2-5) (3 exact solutions returned by solve)
solve((1/2)^x=-x^2+3) (2 approx solutions)
solve(ln(x)=x^2-5) (2 approx solutions)
03-26-2020, 09:03 AM
Post: #5
 Jan 11 Junior Member Posts: 25 Joined: Mar 2020
RE: GEOMETRY application - a problem
I know that CAS super solves all these equations. But the essence of the problem is that the GEOMETRY application does not solve these three equations. Does not graphically find all the solutions. And when I go to CAS to give me solutions, he only gives me the ones that GEOMETERS found. See it in the attached example.

03-26-2020, 10:09 AM
Post: #6
 parisse Senior Member Posts: 1,187 Joined: Dec 2013
RE: GEOMETRY application - a problem
Indeed, the equation is rewritten differently and that raised an undef which was not correctly handled by the bisection solver. I fixed the source code.
By the way, for the geometry app, you can also report with commandlines to help me reproduce the problem:
GA:=plotfunc((1/2)^x);GB:=plotfunc(-x^2+3);GC:=inter(GA,GB);coordinates(GC)
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