Suppose you have 4 legs of a table
you need to rotate a certain angle each leg - but there is symetry here
is there a fast way of doing it for one leg and the other ones would adjust in consequence function of the first leg angles 
Tanks & Salutations
Create one lag and angle it as needed. in edit mode from the top view move the leg to one corner. Add a mirror modifier this will mirror the leg across the x axis now add a second mirror modifier and click the y button to mirror it across the y axis. Apply both modifiers and you should be all set.
Maybe work with 1/4 of the table and one leg, and add two mirror modifiers? I’m not quite sure this is what you’re asking though.
Edit: Yeah, what ReeVee said first.
OK i was more tinking of having some flexibility
Mirror is great when you know that the first is OK then you can go
Now if you want to re-adjust the angle of one leg you have to redo the 2 mirror again?
I would also like some flexibility in the sense that when you change one leg all the other would follow with proper angles !
How about using some sort of track to or constraint ?
Salutations
No, it’s a mirror MODIFIER. It’ll mirror it in real-time, you can keep on editing and it’ll keep updating the changes automatically.
EDIT: And if you rotate the vertices of the leg instead of the leg object, you should have no problems at all.
Can you elaborate on the difference between rotating vertices or the object itself ?
Tanks
If tou rotate the object you will alter its local axis direction which then means the mirror axis will no longer be aligned to the global axis. Also you cant move the leg vertices while leaving the tabletop vertices if you rotate in object mode.
Do not apply the mirror modifiers. This way any changes you make to the first lag will be symmetrically applied to the other legs. This includes changes in angle, size or any vertex editing.
Note: the other lags do not real exist but are only mirrored images of the first leg until you apply the mirror modifier’s.