Find / Solve definition issue

[JBlackhole]

To all

Dug out an old mcad sheet and was hoping to had a "check" but I am having a problem in properly defining either a Find or use the solve option. It's very embarrassing 

Can someone advise the mistake I made in setting either option? see attached mcad 15 sheet

Thanks

Regards

[Werner_E]

Looks like you have a typo in your sheet. You defined "ft2" but used "fty" for solve and the solve block.

The symbolics will not find a solution even if you change "fty" to "ft2" but the solve block gives you happily the solution 249.995. You also may use the "root" command in one of its two flavors to solve for the variable.

[JBlackhole]

Thanks. This is very embarrassing! A copy-paste and not paying attention!

Out of interest: Why does the symbolic solve does not work in this case?

 if one does 1 - (expression in bracket)=0 then Solve find a solution. It's an imaginary with the real part =-249.976

(Even if I force assume ,s=real)

Thanks

[Werner_E]

Mathcad's symbolics is rather weak since they replaced Maple by muPad with version 14.

The symbolics solver is known to ignore assume-statements when its "forced" (by an equation it can't solve analytically) to switch into numerics mode.

Its also no unusual that a simple manual help like putting all on one side of the equations as you had done helps the symbolics enough to turn an unsolvable equation into a solvable one.

Its nice that Mathcad includes symbolics but symbolic calculations are not the main business of the program, its just a nice-to-have.

BTW, I was not able to duplicate what you wrote. The solvee still will run "forever"

[JBlackhole]

Thanks. I don't use the solve that often. I tried because I saw some rather good stuff done by users like yourself , LucMeekes to mention only two of them

Got this

but I did notice that I also get the "infinite" looping issue. As the Find (or root as suggested) work fine I'll drop the Solve option

[Werner_E · Accepted solution]

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@JBlackhole wrote:

Thanks. I don't use the solve that often. I tried because I saw some rather good stuff done by users like yourself , LucMeekes to mention only two of them

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Of course I like symbolic solutions very much as they are exact and more general and useful in more ways than a single numeric solution.

But the symbolics reaches its limits quite quickly when it gets more and more complex and for technical applications a numeric solution often is all thats needed.

Luc BTW is still using Mathcad 11 and so he is still enjoying Maple as symbolics engine rather than MuPad. So he often is able to find symbolic solutions where users of Mathcad 15 or Prime have to lay down their arms.