Mathcad Express Prime 3.1 - Handling Equations

[jlovegrove-2]

Many years ago I used MathCad 2.5 and in this one could type in an equation with essentially anything on either side, use a colon as the equal sign and give the equ command.  It did not restrict what you did and there was no attempt to evaluate a variable or expression or assign a value.  On could then go through and modify/manipulate the equation to simplify etc.

Having downloaded the above on a trial basis with a view to buying a licence, I find that this cannot be done,  there seem to be no options other than using = to find the value of a variable or expression or : to assign a value.

Is there any way of just being able to write an equation without either of the above occurring?

[MJG]

I think you want the Boolean comparison "equal to".  You can find it under Operators -> Comparison, or you can hold Ctrl and press =.

[MJG]

Also, note that Mathcad can automatically simplify equations or solve for a given variable (no need to manually modify/manipulate).

(examples shown in Mathcad 15, but Prime 3.1 is similar)

[Fred_Kohlhepp]

Will Express (aka Free and limited) do that?

[LucMeekes]

Nope, express will offer access to symbolics and other advanced features (such as solve blocks) only for a limited time.

But you should be able to just type in equations with the boolean equals symbol.

Luc

[VladimirN]

LucMeekes wrote:

Nope, express will offer access to symbolics and other advanced features (such as solve blocks) only for a limited time...

30-day full functionality option.

[jlovegrove-2]

Thanks Mark and Luc,

Using the Ctrl = solved the problem I can now do what I wanted to do. I looked through all the help stuff and could not find anything referring to this..I will also try to use the simplify facility in my equation manipulation.

Looking at Luc's response, it it is interesting that someone else remembers version 2.5 (which you have to run in DOSBox in the later versions of Windows.)  It was a very robust program compared with the early Windows versions (e.g. 4 ) that were close to useless.

Thanks again

John

[LucMeekes]

Ah, found what you're referring to. Here's Mathcad 2.50:

It is possible because I set the program to manual, that is, I enforced manual recalculation. In order to calculate I have to press the F9 key. And if I do that, mathcad complains that x is undefined for the equation that starts with 12*x...

You can get a similar effect in Prime if you click the "Stop All Calculations" button in the controls section of the Calculation Tab of the Ribbon.

HOWEVER: Prime will not allow you to enter equations like the second and third shown above, because it maintains that you cannot assign an expression to a calculation; which is a reasonable restriction. Also recent versions of Mathcad (no Prime) will not allow that. I don';t know when this was abandoned, but it may have been thrown out already at version 3 (Mathcad, not Prime).

So if you still want to enter just expressions and to the manipulations yourself, use the boolean equals [CTL-=] to write your equations. And as Mark has shown, recent versions of Mathcad, and also Prime, have the ability to symbolically work such expressions.

I haven't found the "EQU" command in Mathcad 2.50 yet. What would it do?

Success!
Luc

[LucMeekes]

Ah, found it. It's called "eq" and esentially sets to disable evaluation of the expression. It appends a small box at the end of the equation.

Disable evaluation is still available in modern versions of Mathcad and in Prime it's referred to as "Disable region", but you don't need it if you use the boolean equals symbol to define your equations.

Luc

[jlovegrove-2]

I was just going to point out how to use equ in 2.5. (cursor in the equation then Esc and type equ)  it toggles between enabled and disabled.

I tried using Disable Region in the new version and it works if you have something like a := b+c where b and c are not defined.  However it will not allow you to put in something like a + b := c + d    but using the Ctrl = for the equal sign does.

John