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# mathematical expression from string input

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Md. Ashikur Rahman Any on 17 Apr 2021
Commented: Stephan on 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
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### Accepted Answer

Stephan on 17 Apr 2021
Edited: Stephan on 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)
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Stephan on 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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