mathematical expression from string input

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

Answer 1

[Stephan]

https://de.mathworks.com/help/symbolic/str2sym.html

>> 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)

[Md. Ashikur Rahman Any]

Thanks.It worked .

How to plot this sym function like this way and get intersecting point.

[Stephan]

Note that you have to rewrite e^x to exp(x) in you string input:

syms x a
fun = str2sym("(sin(sqrt(x)+a) * exp(sqrt(x))) / sqrt(x)")
fun = subs(fun, a, 1)
intersect = solve(fun==0)
fplot(fun)

[Md. Ashikur Rahman Any]

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]

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--')