Taylor's series method to solve first order first degree ODE

14 次查看(过去 30 天)
Can someone help with how to solve first order first degree ODE using Taylor's series method? I am able to find derivatives but unable to substitute the values at given initial condition.
I have typed the code as below,
clear
clc
syms x y(x)
x0 = 0;
y0 = 1;
y1 = x^2*y-1;
y2 = diff(y1);
y3 = diff(y2);
y4 = diff(y3);
y10 = subs(y1,x,0);
y20 = subs(y2,x,0);
y30 = subs(y3,x,0);
y40 = subs(y4,x,0);
%Taylor's Method
y = y0 + (x-x0)*y10 +(((x-x0)^2)/2)*y20 + (((x-x0)^3)/6)*y30 + (((x-x0)^4)/24)*y40
And the output is as below.
substitution at x=0 is not working. Kindly help.

回答(2 个)

VBBV
VBBV 2023-5-27
编辑:VBBV 2023-5-27
Use taylor function
clear
clc
syms x y(x)
x0 = 0;
y0 = 1;
y1 = x^2*y-1;
y2 = diff(y1);
y3 = diff(y2);
y4 = diff(y3);
y10 = subs(y1,x,0);
y20 = subs(y2,x,0);
y30 = subs(y3,x,0);
y40 = subs(y4,x,0);
%Taylor's Method
% y = y0 + (x-x0)*y10 +(((x-x0)^2)/2)*y20 + (((x-x0)^3)/6)*y30 + (((x-x0)^4)/24)*y40
% use taylor
y = y0+taylor(x^2*y-1,x,'ExpansionPoint',0)
y(x) = 
  4 个评论
Shrivatsa Joshi
Shrivatsa Joshi 2023-5-30
If you consider taylor function after first term (y0), the coefficient of y'(0) will be taken as 1, which is wrong. The coefficient of y'(0) should be x.
And moreover taylor function can be used on known function in MATLAB to expand. Not to find the unknown function.
VBBV
VBBV 2024-12-10
@Shrivatsa Joshi ok. agreed but why do you think subs is not working. In your program, x has been defined as symbolic variable initially and used again in the expansion equation after substituting it with 0. So, whenever variable x is called symbolic toolbox treats it as new unknown (independent) variable.
clear
clc
syms x y(x)
x0 = 0;
y0 = 1;
y1 = x^2*y-1;
y2 = diff(y1);
y3 = diff(y2);
y4 = diff(y3);
y10 = subs(y1,x,0)
y20 = subs(y2,x,0)
y30 = subs(y3,x,0)
y40 = subs(y4,x,0)
%Taylor's Method
y = y0 + (x-x0)*y10 +(((x-x0)^2)/2)*y20 + (((x-x0)^3)/6)*y30 + (((x-x0)^4)/24)*y40
% use subs after completing the equation of taylor expansion terms.
y = subs(y,x,0)

请先登录,再进行评论。


Oper
Oper 2025-10-15

Consider the initial value problem given by the ODE dy dt = y − t 2 + 1, y(0) = 0.5. a. Use the Taylor Series Method (up to the second order) to derive the Taylor series expansion for the solution of the ODE around t = 0. Calculate the first few terms of the series. b. Implement the Taylor Series Method in MATLAB to approximate the solution over the interval t = [0, 2] and plot the result. c. Use the Second and Fourth-Order Runge-Kutta method to numerically solve the same ODE over the interval t = [0, 2] and plot solutions on the same graph as the Taylor Series approx- imation. d. Compare the three numerical methods based on their accuracy and computational efficiency, and discuss scenarios where one method may be preferred over the other.

类别

Help CenterFile Exchange 中查找有关 Calculus 的更多信息

Community Treasure Hunt

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

Start Hunting!

Translated by