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mathematical expression from string input

조회 수: 20 (최근 30일)
Md. Ashikur Rahman Any
Md. Ashikur Rahman Any 2021년 4월 17일
댓글: Stephan 2021년 4월 19일
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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Stephan
Stephan 2021년 4월 17일
편집: Stephan 2021년 4월 17일
>> 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)
  댓글 수: 4
Md. Ashikur Rahman Any
Md. Ashikur Rahman Any 2021년 4월 18일
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 2021년 4월 19일
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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