variable in matrix format, where one is dependent on all the others, Possible?

[AC_10816299]

Using Mathcad Prime 8.0.
I am trying to define a variable in a matrix format, where variable has an index i= 1,2,..5.
I am able to define all variables, but cannot use a single entry, let's say d5. What is the proper way of defining my variable in such case? I tried with both matrix and table, getting same, "underdefined" fail. 

I also would like one oth the variables to depend on the others, namely l3=h-l1-l2-l4-l5(these are partial lengths of the entire hight of construction). Can one define such variables in Mathcad Prime? 

[LucMeekes · Accepted solution]

You have to type [ to get an index, not Ctrl _.

That applies both to the definition of d[I, as well as to its usage in d[5.

There are other observations. See attachment.

Success!

Luc