Programming function Mathcad 15

Stuart uses the symbol in the 'if' statement

which is the mathematical notation for a logic AND operator, simply because multiple conditions need to be satisfied simultaneously.

(just like there is the OR: that you can use when one of a number of conditions needs to be true)

They are found on the pallette with boolean symbols.

Now to your:

There are two types of subscripts used in Mathcad. Real and literal. Real subscripts are used to point to elements of a vector or matrix, as Stuart explained following his explanation on programming. The other type of subscripts is a literal subscript, which just puts part of the variable name in the subscript position. You type it by using a dot: '.'. So if you type a variable name in with: A.b, you get .

You cannot nest literal subscripts. Typing A.b.c gives you . Notice that the second dot gets visible as a dot.

When you type A.b,c you get . This means you're addressing the c'th element of the vector A.b. Essentially there are two variables here, separated by the comma: the vector A.b and the (index) variable c.

You can, if you really want to, embed a comma in a subscript, without it meaning the separation of two variables. By pressing [CTL-SHFT-k] you enter symbolic entry mode where you can enter symbols that show. To exit symbol entry mode press [CTL-SHFT-k] again. So to enter the DeltaSess,k variable as a single variable you should type:

D[CTL-g]S.ess[CTL-SHFT-k],[CTL-SHFT-k]k.

{The [CTL-g] is to convert from d to delta.}

Success!
Luc