mathematical expression from string input
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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
采纳的回答
>> 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 个评论
Md. Ashikur Rahman Any
2021-4-17
Thanks.It worked .
How to plot this sym function like this way and get intersecting point.
Stephan
2021-4-17
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
2021-4-18
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
2021-4-19
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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