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Solving the equation

Ravii
4-Participant

Solving the equation

Hi, I'm new to Mathcad. I understand the basics, but I'm struggling with how to solve the equation to find the value of x
Mathcad prime 09

Ravii_0-1719300682082.png

 

1 ACCEPTED SOLUTION

Accepted Solutions
MartinHanak
24-Ruby II
(To:Ravii)

Hi,

what about this?

MartinHanak_0-1719306244360.png

 


Martin Hanák

View solution in original post

11 REPLIES 11
VladimirN
24-Ruby II
(To:Ravii)

Ravii
4-Participant
(To:VladimirN)

Do I have write Solve ?

Ravii_0-1719303831186.png

 

Cornel
18-Opal
(To:Ravii)

Cornel_0-1719306406088.png

Ravii
4-Participant
(To:Cornel)

Thank you Cornel.

ttokoro
20-Turquoise
(To:Ravii)

image.png

MartinHanak
24-Ruby II
(To:Ravii)

Hi,

what about this?

MartinHanak_0-1719306244360.png

 


Martin Hanák
Ravii
4-Participant
(To:MartinHanak)

Thank you Martin for the solution, really helpful

Ravii
4-Participant
(To:MartinHanak)

Is it possible to get unit mm in the final answer ?

MartinHanak
24-Ruby II
(To:Ravii)


@Ravii wrote:

Is it possible to get unit mm in the final answer ?


Hi,

MartinHanak_0-1719311748746.png

 


Martin Hanák

Hi,

my the last "picture".

MartinHanak_0-1719312416310.png

 


Martin Hanák
Werner_E
24-Ruby V
(To:Ravii)

@Ravii 

Some remarks ahead:

1) In your equation you are consequently missing the multiplication dots. That way an expression like b(x^2) is interpreted as applying the (non-existent) function b to argument x^2 and of course will fail:

Werner_E_0-1719317386566.png


2) You defined a variable "m". Thats not a failure as it is correctly labelled as "Variable" and so you still an use the unit "m". But when you try to use the symbolic "solve" you my get into troubles. So I would suggest avoiding unit names for variables, even though its perfectly 'legal' to do so.

 

3) When you intend using the symbolics (I won't suggest doing so here) you should turn on "Units/Constants in Symbolics" in the calculation options and then recalc your sheet.

 

As for solving this simple equation, there are many ways to skin a cat:

 

1) A solve block with "find" (you need to provide a guess value)

Werner_E_1-1719317461065.png

See also here 🙂 : Re: Calculation of weld design

 

2) The "root" function with a guess value

Werner_E_2-1719317504621.png

 

3) The root function, providing limits for the variable you are looking for

Werner_E_3-1719317565340.png

 

4) The symbolic "solve". It can be a bit tricky to filter for the positive solution. I won't recommend using the symbolics here

Werner_E_4-1719317997023.png

 

5) You may define a function dependent on all the involved variables in front of the variable definitions (or you use clear.sym(...) to make the definitions invisible for the symbolics)

Werner_E_5-1719318299925.png

and later use this function to calculate x. You still would have to take measures if you just are interested in the positive solution.

The advantage of this way is that you could quickly compare the results with different input values:

Werner_E_0-1719318796893.png

 

Prime 9 sheet attached

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