why dont Intersect not working in newest version of geogebra

Liamms shared this question 2 years ago
Answered

The intersect tool doesn't work in the newest version if i try to intersect a circle and a line.

Comments (14)

photo
1

Please post your .ggb file

photo
1

Similar problem:

Intersect does not work for these two objects: f(x)=80*1.2^x and y=500

Version 6.0.605.0-offline

photo
2

Interesect() has several syntaxes. Try

Intersect(f, g, 9, 11)

photo
1

That works - thank you!

I teach pupils without much experience in GeoGebra. I usually teach them to use the intersect-button instead of the command. I am afraid it wil be a bit too "technical" for my demographic. Maybe not when I demonstrate and explain, but probably if they encounter this problem on a test.

I noticed that when I use the intersect-button, the algebra field returns (f, g, x-value of last clicked point, y-value of last clicked point) instead of start x-value and end x-value. I guess there is a logic to it somehow, but I can't help but wonder if it could be an error.

A collegue tested an older version of GeoGebra (5.0.321) and he tells me it worked on that one. In my case it would be great to have it back working like that, but I understand if other needs are more important. No need to make a big deal of this it doesn't affect many others.

Thank you for your time!

photo
2

Try

f(x) = 80*1.2^x
g(x) = 500

photo
1

Wow!

That is the best solution yet: Just replacing "y=500" with "g(x)=500" did the trick!

Thank you :-)

photo
photo
2

Intersect doesn't always provide you a solution (that's because of how things are calculated internally). If you don't get a solution that way you can try the command Solutions( f = 500) which gives you the solution l1={10.05}

photo
1

Thank you. This also works.

My own workaround with my students was to solve it as an equation in CAS (NSolve 80*1.2^x = 500), but in doing so I felt that the visual effect was lost. Well, I still had the lines intersecting on the screen, so they knew what I was going for, but they were left with an impression that GeoGebra is difficult to use. Your solution is a bit better than mine in that regard, but it would still be nice if the intersect would give the answer straight away. My comment is not meant as a disrespect to your helpful answer, but if someone developing the algorithms is also reading this, maybe it is possible to find a way to make intersect work in similar cases?

Thank you for your time!

photo
2

Thanks, we'll improve it soon so that this works!

photo
2

Fixed for next release

photo
2

v612 now released

photo
1

Hi,

Which app's version are you talking about? The classic online version?

Cheers! :)

photo
1

All versions :)

photo
1

:) thanks Michael...

photo
© 2021 International GeoGebra Institute