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Finding result by iteration, error given by FIND function

Patryk
1-Newbie

Finding result by iteration, error given by FIND function

Hello,

I have an equation with one uknown on both sides and would like to iterate to get the value of variable, however the find function brings error, I think I am following others recommendations (several youtube presentations) but still no result. I have more equation like this to solve and would really do with advice what I am doing wrong.

I am new to Mathad.

1 ACCEPTED SOLUTION

Accepted Solutions
Werner_E
24-Ruby V
(To:Patryk)

my understanding was that by selecting find function from menu is actual solve block selection that actually was very wrong understanding. Habit taught by older book to type and use shortcuts for everything shifted my eyes away from the bar with solve block button.

Yes things have changed since mathcad 15 (unfortunately). As find() can't be used outside a solve block, it would be a good idea if Prime would insert a solve block autimatically when find() is inserted outside of a solve block. but thats not implemented that way. You first have to insert that ugly and clumsy block and then add your guesses, constraints and a solve block function like Find, Minerr, Odesolve, etc.

Getting a suitable guess value is sometimes vital. In your case it was obvious that your system of two equations in two variables is in reality just one euqation in one variable. in this case its often a good idea to plot the function to get a visual impression where a solution is to be expected. Your expression gets complex for values of tx greater than 40, so we had to look at the negative range and zoom far out (Prime does not have a zoom option, so its a tedious job changing the plot limits manually.

I haven't used a solve block in my first attempt to get a solution but had used root(). But of course the solve block with your two variables would yield the very same result given you provide suitable guesses.

1.png

2.png

P.S.: There sure are many good ressource out there dealing with Mathcad 15 (still the much superior version) and below. A lot of things may apply to Prime, too - a lot won't and lead to confusion. So for the first steps it may be a good idea to stíck with the help and other specific Prime ressources.

PTC provides some files here which may be of interest:

http://communities.ptc.com/docs/DOC-3931

http://communities.ptc.com/docs/DOC-3621

View solution in original post

7 REPLIES 7
Werner_E
24-Ruby V
(To:Patryk)

In Prime you can't simply type find(), you must insert a solve block.

I have added the solve block by clicking 'find' in Functions->Solving menu, is any other way of doing it? If you put all this effort to aswer and criticise you could as well instruct how to do it correctly.

Werner_E
24-Ruby V
(To:Patryk)

Patryk Halczak wrote:

I have added the solve block by clicking 'find' in Functions->Solving menu, is any other way of doing it? If you put all this effort to aswer and criticise you could as well instruct how to do it correctly.

1) I wasn't criticising but just pointing you to your error.

2) When you start Mathcad, the first thing you see is this:

1.png

So it was hard to imagine for me that you can't find a way how to insert a solve block.

3) You had not written that your help is broken or you otherwise are not able to read or understand Prime's help section. It has to be assumed that when somebody asks a question in this user driven forum, that he has already used other ressources available to him - primarily of course the built-in help, where "To define a Solve Block" can very easily be found.

Despite your impudent reply a last tip: Chose another guess value to get a solution. After all your solution is approx. at -3.187*10^5. With guess value 0 the solve block will fail.

I apologise for my impudence, I spent hours trying to get several things to work in mathcad with prior reading of some older bools and watching YouTube videos. I have also referred to manual but for some reason was blind enough to see the solve block and my understanding was that by selecting find function from menu is actual solve block selection that actually was very wrong understanding. Habit taught by older book to type and use shortcuts for everything shifted my eyes away from the bar with solve block button.

It does not mean that I have not found the solve block and attempted using it before I posted my rude answer. I have tried it with 0 and other guess though did not get any result. That why I was so annoyed, mainly by myself choosing tool I did not know for something important. Though I thought and still think mathcad is great for this simple thing and lot other complicated ones. It was meant to be learning by real practice. Nevertheless please accept my apology, I appreciate your time spent on helping others.

Werner_E
24-Ruby V
(To:Patryk)

my understanding was that by selecting find function from menu is actual solve block selection that actually was very wrong understanding. Habit taught by older book to type and use shortcuts for everything shifted my eyes away from the bar with solve block button.

Yes things have changed since mathcad 15 (unfortunately). As find() can't be used outside a solve block, it would be a good idea if Prime would insert a solve block autimatically when find() is inserted outside of a solve block. but thats not implemented that way. You first have to insert that ugly and clumsy block and then add your guesses, constraints and a solve block function like Find, Minerr, Odesolve, etc.

Getting a suitable guess value is sometimes vital. In your case it was obvious that your system of two equations in two variables is in reality just one euqation in one variable. in this case its often a good idea to plot the function to get a visual impression where a solution is to be expected. Your expression gets complex for values of tx greater than 40, so we had to look at the negative range and zoom far out (Prime does not have a zoom option, so its a tedious job changing the plot limits manually.

I haven't used a solve block in my first attempt to get a solution but had used root(). But of course the solve block with your two variables would yield the very same result given you provide suitable guesses.

1.png

2.png

P.S.: There sure are many good ressource out there dealing with Mathcad 15 (still the much superior version) and below. A lot of things may apply to Prime, too - a lot won't and lead to confusion. So for the first steps it may be a good idea to stíck with the help and other specific Prime ressources.

PTC provides some files here which may be of interest:

http://communities.ptc.com/docs/DOC-3931

http://communities.ptc.com/docs/DOC-3621

Werner,

This all makes sense now, the reason I created second equation was just to have 2 eqations. Because it did not work for me I thought find() requires two variables to work, hence I created second not really needed one.

This solve block really ruins the look of the sheet, is the Prime a current latest version that is going to be contiuously developed or is it just an alternative tool? I really prefer Mathcad 15,is obsolete now?

Thanks for your valubale help, links are very usefull too.

Werner_E
24-Ruby V
(To:Patryk)

Prime was supposed to be the "modern" successor of Mathcad 15. Mathcad was coming into age and so the intention was to give it a modern, more versatile code base (which sure was a good idea and a necessity, too).

Obviously PTC had greatly underestimated that task and was not able or willing to provide the necessary ressources. So Prime in its version 3 still is vastly inferiour compared with Mathcad and there sure is a reason why PTC gives away Mathcad 15 for free when you buy Prime (buy the tail and get the dog for free) and already had announced that this will be so at least until Prime 5 is rolled out. Mathcad 15 is not improved or feature enhanced anymore but is still maintained and bug fixed and the next release is promised to be fit for modern operating systems.

Most experienced users here still continue to work with Mathcad 15 either because of the missing features in Prime, the slow performance or the awkward and cumbersome user interface.

So Mathcad 15 is not obsolete now, but will be some day and the future is either Prime or a competitors product one choses to switch to.

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