CAS ggb5/ggb6 different calculation results

hawe shared this problem 4 years ago

An example session on attached applet

subject: constructing rotation matrix with vector axes

check matrix constuction to matrix formula of wickipedia (line 3)

Todo: Algebra - change rotation angle e.g w = 2 pi/3

I have to recalc the app (the image vectors line 6,8,11) multiple times until the constructed matrix will match wicki matrix. Problems on the way: CAS lines will be overwritten (undo back to correct state), Definition of image vectors ex',ey',ez' will be lost and replaced by other names. Recalculation of an image vector will change other image vectors, but recalculation of a image vector should have no effect to other image vectors.

If I use numeric arguments to w (w=2.25) the app seems to get stable results?

Comments (6)


Sorry, I don't see a difference here. Please can you post a screenshot of the bug?


Start setting w=2pi/5


ex', ey' not correct ez' is correct


recalc ey' ==> ey' correct display off


recalc ex' ===> at least correct rotation matrix


Changing w= 1.884955592154 (3pi/5) I got correct result one step. Some times recalc of one of the exyz' changed an other exyz'. Some sessions need 5-6 recalc until matrix is correct.


Does it help if you define everything in the CAS rather than having some things in the Algebra View?


The only variable term in algebra view is the rotation angle w - I defined an other angle variable in CAS, but it does not help. recalc one ot the exyz' has side effects to an other exyz' - after 4-5 trys I gave up to get a correct rotation matrix.

Numeric arguments will work...


I removed ; in hidden output lines (2,4,9) to test the effect.

set w= 3pi/5


I got a friezed machine (win10 out of order) - mouse dead for a long time - hard to close geogebra - repeated 3 times always with the same result. I had this effect in multiple apps after "Calculation toock too long..." - geogebra does not come back - hanging - stress the whole system with high CPU load...


After relaoding app with no hidden lines in CAS I recognized, that the Points E1,E2,E3 in algebra view do not match E1,E2,E3 in CAS (now become vectors)


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