mathematical expression from string input

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Md. Ashikur Rahman Any
Md. Ashikur Rahman Any am 17 Apr. 2021
Kommentiert: Stephan am 19 Apr. 2021
I want to make a equation solver which will take any type of mathmatical equation as input .and return the roots.For that reason ,first the program need to read the equation.I want to input the equation in string format.then matlab will consider this as a function of x.
for example if i give input as
(sin(sqrt(x)+a) * e^sqrt(x)) / sqrt(x)
Matlab will read this as
and then i will plot the curve ,and the intersecting point with x axis is the solution of the equation.
How to do that?
Thanks in Advance

Akzeptierte Antwort

Stephan
Stephan am 17 Apr. 2021
Bearbeitet: Stephan am 17 Apr. 2021
>> fun = str2sym("(sin(sqrt(x)+a) * e^sqrt(x)) / sqrt(x)")
fun =
(e^(x^(1/2))*sin(a + x^(1/2)))/x^(1/2)
>> pretty(fun)
sqrt(x)
e sin(a + sqrt(x))
-------------------------
sqrt(x)
  4 Kommentare
Md. Ashikur Rahman Any
Md. Ashikur Rahman Any am 18 Apr. 2021
The equation has multiple solution.But it only shows one.
How to show multiple solutions as output.
I know there are infinite number of solution.But if i want to get solution in a sfecific range ,how to get that??
Stephan
Stephan am 19 Apr. 2021
Make assumptions on x and solve then:
syms x a
fun = str2sym("(sin(sqrt(x)+a) * exp(sqrt(x))) / sqrt(x)")
fun = subs(fun, a, 1)
assume([x>25, x<30])
intersect = solve(fun==0)
fplot(fun,[25,30])
xline(double(intersect),'k--')
yline(0,'k--')

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