viva.amego shared this idea 11 years ago
adding constrains to object would be nice and very helpful
like "Segment[A, B, poly1] " would add length constrain "length=5" so whatever the position of points A and B length between A and B will always be 5
and this is done by narrowing the domain of the elements by the condition of constrain
constrains can be for :
*belong (element to)
and so on
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As Noel has indicated, this isn't how GeoGebra works (so we won't be adding this) - you just need to make your construction in a different way.
thanks for the reply but what i am trying to say is some times i need to create entities with unchangeable properties like making a polygon in the shape of kite i can easily construct the kite but if i need to re-size it or move any point of the polygon i need to reconstruct the kite from the beginning
so i thought it would be much easier if it's one of the polygon properties that 2 adjacent sides are equal so when never i need to change position of points around the polygon remain kite
thanks for the reply but as i mentioned when i replied to Noel that i need entities or constructions with specific properties (fixed properties) so if there is another way to do it i would be grateful if you tell me how
As already evocated in the precedents posts,it is you which add contrains in your construction, not the software because each of us have differents contrains
Use slider (names a,b , c )to change dimensions from one to an other construction
B=A+(a,0) give you a variable lenght contrained by you (a=5)
Try to build the polygons in a circle of radius 'the slider a) which will be used to change the lengths, areas, angles ...
First point A of your construction is used to move the construction and the others points follow the point A in function of your constrains
And with the version 4 you can paste and copy a select construction
thanks for the reply but i didn't really understand what you meant by
all what i meant from this post that what about having angles and lengths as independent variables (free object) not just points
If I understood, you need to maintain a polygon shape after resizing.
Why don't you resize the polygon using a linear transformation?
For example, you could use a dilation, selecting the Enlarge Object from Point by Factor tool, and applying it to your polygon.
(btw, if you build an object using "compass and ruler" methods, it maintains its geometrical properties after resizing)
I know only one dynamic geometry software that works with constraints: Geometry Expressions.
However, it's not free!
Best regards, Humberto.
TI Nspire can have restraints as well. I agree that this isn't how GG works, and that it confuses the idea of independant objects (though IF you could add lengths and angles as independant objects this would bi very nice...)
One thing that is beautifully done with constrants in TI Nspire is an ellipse. Create 3 points. Measure and add two sides and lock this value. When moving the point between the two measured sides it will trace an ellipse.
TI Nspire is not free, nor is it generally as good as GG IMHO, but this feature is attractive. To creati it I assume you would have to make a list of object afffected by constraints, and when any of these are moved the displacement in y is tested numeriacally to fit with the constraint. Perhaps something one could add oneself with clever scripting when it is needed.
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