oops. submitted too fast.
in this bug, square brackets and perens do not fully encompass the matrix, nor
do they fully encompass a fairly large division or any complex object that is
large that it (hopefully) is supposed to encompass.


also, try this:
z=100 cdot ( { [ matrix{1 # 2 # 3 # 4 ## 5 # 6 # 7 # 8 ## 9 # 10 # 11 # 12 ## 13
# 14 # 15 # 16} ] }  over {123 cdot lline cos(x)  rline }  )

in this equation it is woefully apparent that better brackets are needed. 
forget whether the math is valid or not.  
Jim Michaels

Use scalable perens left( and right) or left[ and right] like this:

left[matrix{1 # 2 # 3 # 4 ## 5 # 6 # 7 # 8 ## 9 # 10 # 11
# 12 ## 13 # 14 # 15 # 16} right] newline
left(matrix{1 # 2 # 3 # 4 ## 5 # 6 # 7 # 8 ## 9 # 10 # 11 # 12 ## 13 #
14 # 15 # 16} right) newline
z=100 cdot left( { left[ matrix{1 # 2 # 3 # 4 ## 5 # 6 # 7 # 8 ## 9 # 10 # 11 #
12 ## 13
# 14 # 15 # 16} right] }  over {123 cdot lline cos(x)  rline }  right)

Closed.

then please consider changing all the perens and brackets' definitions in the 
selection toolbar.  the other kind of brackets shouldn't exist.  the only kind 
that should exist are the ones that encompass large objects.  I can't see any 
reason for keeping anything else.

it just messes things up for every non-expert.
Jim Michaels

I do not agree. Many people just need the non-scalable brackets because they do
not create complex formulas. Also the symbols in the Selection toolbox are made
differently to recognize and even have the keyword "scalable" in the tool tip.

But: we can keep your proposal as "Enhancement" and let the community decide
about this.

I just thought of something that will allow you to keep the other brackets:  
simply swap the upper set of brackets/perens with the lower set of 
brackets/perens.  

why: people instinctively go toward the top (like me), and all the extra copies 
simply confuse (Or I think I don't need that).  when I actually try it out and 
I get cheesy results, I/others get upset with the software.  by default, make 
the scalable brackets available at the top and the non-scalable brackets at the 
bottom.

Also consider that if you do remove the non-scalable brackets and perens, It 
would be really nice to be able to use simply [ ] instead of left[ right]  but 
if you did make such a change, file compatibility with older versions or even 
being able to open old files will need to be reinterpreted.  both types of 
syntax will need to be parsed as the same thing: scalables.