topic Re: Solving the equation in Mathcad

Solving the equation

Ravii — Tue, 25 Jun 2024 07:35:12 GMT

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

Re: Solving the equation

VladimirN — Tue, 25 Jun 2024 08:01:26 GMT

From "Help Center" - "To Solve Equations Symbolically": https://support.ptc.com/help/mathcad/r10.0/en/index.html#page/PTC_Mathcad_Help/to_solve_equations_symbolically.html

Re: Solving the equation

Ravii — Tue, 25 Jun 2024 08:24:00 GMT

Do I have write Solve ?

Re: Solving the equation

MartinHanak — Tue, 25 Jun 2024 09:04:14 GMT

Hi,

what about this?

Re: Solving the equation

Cornel — Tue, 25 Jun 2024 09:07:06 GMT

Re: Solving the equation

Ravii — Tue, 25 Jun 2024 09:14:54 GMT

Thank you Cornel.

Re: Solving the equation

Ravii — Tue, 25 Jun 2024 09:15:25 GMT

Thank you Martin for the solution, really helpful

Re: Solving the equation

ttokoro — Tue, 25 Jun 2024 09:26:04 GMT

Re: Solving the equation

Ravii — Tue, 25 Jun 2024 09:38:26 GMT

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

Re: Solving the equation

MartinHanak — Tue, 25 Jun 2024 10:36:05 GMT

@Ravii wrote:

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

Hi,

Re: Solving the equation

MartinHanak — Tue, 25 Jun 2024 10:47:10 GMT

Hi,

my the last "picture".

Re: Solving the equation

Werner_E — Tue, 25 Jun 2024 13:33:20 GMT

@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:

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)

See also here 🙂 : Re: Calculation of weld design

2) The "root" function with a guess value

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

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

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)

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:

Prime 9 sheet attached