Square Brackets in Textbook mode

[tim_crouse]

What is the deal with the +/- symbol being added when a set of square brackets is added to an equation?

-Tim C.

[rawi]

Hi Tim,
square brackets are not for equations but for matrices and curly brackets are for lists. If you put a +/- in front of a square bracket all elements of the matrix are multiplied with -1

[jonmoore]

It's worth bearing in mind that much as multiple bracket types (accurately) exist in school algebra problems; when working with computer algebra systems (including those on calculators), you only use ( ). There's no hierarchy of bracket types, you simply nest the standard brackets.

The reason for this comes down to semantic meaning in digital systems. Symbols can't be used in a manner that's ambiguous to the system. Each symbol has a specific meaning to the system e.g. on the prime { } are reserved for lists, [ ] are reserved for matrices (and vectors) and outside of order of operations in algebraic expressions ( ) are reserved for complex number entry (many Prime users stick to 3+4i, but (3,4) is a convenience).

Of course, there's a certain ambiguity in the fact that ( ) brackets are used for both order of operations in algebraic expressions and complex number entry, but this ambiguity was less of an issue in the past given that the vast majority of HP calculators were RPN/RPL models. Plus, when using complex numbers within larger algebraic problems, it's usual to first assign your complex number values to variables.

[tim_crouse]

Awesome answers, Thank You.

I was just blindly entering the equation square brackets and all. Good to know their primary use now.

Thanks Again
-Tim C.

[Wes Loewer]

(06-09-2022 12:08 AM)tim_crouse Wrote:  What is the deal with the +/- symbol being added when a set of square brackets is added to an equation?

As others mentioned, the square brackets are for vectors and matrices. Pressing Shift-5 once gives you a vector. Pressing Shift-5 a second time gives you a matrix.

The +/- symbols placed within the brackets are for increasing and decreasing the number of rows or columns in the matrix. Move the cursor to the +/- symbol and press the + key to add a row or column. Press the - key to remove a row or column.