math equation solve issue

[J_power]

Hi experts,

Does anyone know how to solve this issue?

the system show that it couldn't find the answer.

any useful method that can help me to solve this?

[terryhendicott · Accepted solution]

Hi Jason,

If every variable except Tr2 is defined you could use the root() function or a solve block.

Cheers

Terry

[J_power]

Hi @terryhendicott ,

Yes, every variable except Tr2 is defined.

I try to follow your method and I get the result.

but, why Mathcad can't help to arrange the equation if there is a sine in there.

[Werner_E]

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I try to follow your method and I get the result.

If a numerical result is desired, its probably better to use numerical methods like the "root" function or a solve block with "Find".

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but, why Mathcad can't help to arrange the equation if there is a sine in there.

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Again, why do you think that Mathcad should be able to do?

Apart from the fact that the symbolics in Mathcad and even worse in Prime is not state of the art compared to other current software products, its also a fact that by far not all mathematical equation have a closed, symbolic solution.  Actually most haven't 😉

[J_power]

OK, I knew it, thanks.

by the way, what do your mean solve block with "Find"

my method is wrong?

[Werner_E]

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by the way, what do your mean solve block with "Find"

Different ways to solve an equation with Mathcad

Remark:

A solve block with "find" can also be evaluated symbolically (no guess needed)

Using a solve block has the advantage that you can add additional constraints which sometimes might (no guarantee) be betters respected than an "assume" modifier.

[J_power]

@Werner_E 

Many thanks.

it is very clear to me.

[Werner_E]

Why do you think that a generic symbolic solution would even exist?

You won't even find a symbolic solution for a much simpler equation like sin(x+1)=a*x

[J_power]

Hi @Werner_E 

Because I think the answer exists, and I can get a math equation.

Now, I understand! thanks for your explanation.

[Werner_E]

O don't think that a closed symbolic solution for your equation exists, but if it does, it sure would have to contain a myriad of "if's" concerning the other variables and their values with respect to each other.

The simple equation sin(x)=a*x+b can have (depending on a) none to any finite number of solutions (but not infinite!) if b>1 or b<-1, but it can have at least 1 up to infinite solutions if -1<=b<=1.

How would all these cases be expressed in one single symbolic solution?

[J_power]

got it.

it is more clear to me.

many thanks,