7.24.1 problem 11

Internal problem ID [601]
Book : Elementary Differential Equations. By C. Henry Edwards, David E. Penney and David Calvis. 6th edition. 2008
Section : Chapter 5. Linear systems of differential equations. Section 5.3 (Matrices and linear systems). Problems at page 364
Problem number : 11
Date solved : Saturday, March 29, 2025 at 04:59:06 PM
CAS classification : system_of_ODEs

\begin{align*} \frac {d}{d t}x \left (t \right )&=-3 y \left (t \right )\\ \frac {d}{d t}y \left (t \right )&=3 x \left (t \right ) \end{align*}

✓ Maple. Time used: 0.127 (sec). Leaf size: 34

ode:=[diff(x(t),t) = -3*y(t), diff(y(t),t) = 3*x(t)]; 
dsolve(ode);
 

\begin{align*} x \left (t \right ) &= c_1 \sin \left (3 t \right )+c_2 \cos \left (3 t \right ) \\ y \left (t \right ) &= -c_1 \cos \left (3 t \right )+c_2 \sin \left (3 t \right ) \\ \end{align*}

✓ Mathematica. Time used: 0.002 (sec). Leaf size: 39

ode={D[x[t],t]==-3*y[t],D[y[t],t]==3*x[t]}; 
ic={}; 
DSolve[{ode,ic},{x[t],y[t]},t,IncludeSingularSolutions->True]
 

\begin{align*} x(t)\to c_1 \cos (3 t)-c_2 \sin (3 t) \\ y(t)\to c_2 \cos (3 t)+c_1 \sin (3 t) \\ \end{align*}

✓ Sympy. Time used: 0.069 (sec). Leaf size: 32

from sympy import * 
t = symbols("t") 
x = Function("x") 
y = Function("y") 
ode=[Eq(3*y(t) + Derivative(x(t), t),0),Eq(-3*x(t) + Derivative(y(t), t),0)] 
ics = {} 
dsolve(ode,func=[x(t),y(t)],ics=ics)
 

\[ \left [ x{\left (t \right )} = - C_{1} \sin {\left (3 t \right )} - C_{2} \cos {\left (3 t \right )}, \ y{\left (t \right )} = C_{1} \cos {\left (3 t \right )} - C_{2} \sin {\left (3 t \right )}\right ] \]