Clear Filters
Clear Filters

how to use solve

2 views (last 30 days)
alize beemiel
alize beemiel on 6 Apr 2023
Commented: alize beemiel on 6 Apr 2023
hi ; i need help
I have this equation with 2 parametres a and b
syms b x a
solve ((2*cos(x) - b*(sin(x) + sin(a*x))) == 0) %chooses 'x' as the unknown and returns
I use solve but it return
Warning: Cannot find explicit solution.
  1 Comment
VBBV
VBBV on 6 Apr 2023
Moved: VBBV on 6 Apr 2023
Consider these input values for a and b, for which solve function cant handle the solution. In such cases, use vpasolve to solve equation numerically as recommended by Matlab
syms x real
a = 4; % assume some value
b = 1.5; % assume value
sol=solve ((2*cos(x) - b*(sin(x) + sin(a*x))) == 0,[x]) %
Warning: Unable to solve symbolically. Returning a numeric solution using vpasolve.
sol = 
0.31726439340850840945560345483897
sol = vpasolve((2*cos(x) - b*(sin(x) + sin(a*x))) == 0,[x])
sol = 
0.31726439340850840945560345483897

Sign in to comment.

Accepted Answer

VBBV
VBBV on 6 Apr 2023
syms b x a
sol=solve ((2*cos(x) - b*(sin(x) + sin(a*x))) == 0,[x a b])
sol = struct with fields:
x: [2×1 sym] a: [2×1 sym] b: [2×1 sym]
%chooses 'x' as the unknown and returns
sol.x
ans = 
sol.a
ans = 
sol.b
ans = 
  5 Comments
alize beemiel
alize beemiel on 6 Apr 2023
this is what i want by using matlab
alize beemiel
alize beemiel on 6 Apr 2023
thank you Sir ..for your help and your time

Sign in to comment.

More Answers (1)

Chunru
Chunru on 6 Apr 2023
There is no close form solution when a and b are arbitrary constant for the equation.
If you want to find the numerical solution of the equation with specified a and b, you can use vpasolve:
syms b x a
solve ((2*cos(x) - b*(sin(x) + sin(a*x))) == 0)
Warning: Unable to find explicit solution. For options, see help.
ans = Empty sym: 0-by-1
a = 2; b=0.1;
vpasolve ((2*cos(x) - b*(sin(x) + sin(a*x))) == 0) %chooses 'x' as the unknown and returns
ans = 
7.7984925986314595610243884059956
  3 Comments
Chunru
Chunru on 6 Apr 2023
MATLAB tell you that its solver could not find the explicit solution.
alize beemiel
alize beemiel on 6 Apr 2023
thank you for all
i will try to use Newton Raphson Methode maybe its give me an approximate solution

Sign in to comment.

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!