74.21.7 problem 22 (a)

Internal problem ID [16574]
Book : INTRODUCTORY DIFFERENTIAL EQUATIONS. Martha L. Abell, James P. Braselton. Fourth edition 2014. ElScAe. 2014
Section : Chapter 5. Applications of Higher Order Equations. Exercises 5.3, page 249
Problem number : 22 (a)
Date solved : Monday, March 31, 2025 at 02:59:24 PM
CAS classification : [[_2nd_order, _linear, _nonhomogeneous]]

\begin{align*} x^{\prime \prime }+x&=\cos \left (\frac {9 t}{10}\right ) \end{align*}

With initial conditions

\begin{align*} x \left (0\right )&=0\\ x^{\prime }\left (0\right )&=1 \end{align*}

✓ Maple. Time used: 0.040 (sec). Leaf size: 17

ode:=diff(diff(x(t),t),t)+x(t) = cos(9/10*t); 
ic:=x(0) = 0, D(x)(0) = 1; 
dsolve([ode,ic],x(t), singsol=all);
 

\[ x = \sin \left (t \right )-\frac {100 \cos \left (t \right )}{19}+\frac {100 \cos \left (\frac {9 t}{10}\right )}{19} \]

✓ Mathematica. Time used: 0.127 (sec). Leaf size: 96

ode=D[x[t],{t,2}]+x[t]==Cos[9/10*t]; 
ic={x[0]==0,Derivative[1][x][0 ]==1}; 
DSolve[{ode,ic},x[t],t,IncludeSingularSolutions->True]
 

\[ x(t)\to \sin (t) \left (-\int _1^0\cos \left (\frac {9 K[2]}{10}\right ) \cos (K[2])dK[2]\right )+\sin (t) \int _1^t\cos \left (\frac {9 K[2]}{10}\right ) \cos (K[2])dK[2]-\cos (t) \int _1^0-\cos \left (\frac {9 K[1]}{10}\right ) \sin (K[1])dK[1]+\cos (t) \int _1^t-\cos \left (\frac {9 K[1]}{10}\right ) \sin (K[1])dK[1]+\sin (t) \]

✓ Sympy. Time used: 0.083 (sec). Leaf size: 22

from sympy import * 
t = symbols("t") 
x = Function("x") 
ode = Eq(x(t) - cos(9*t/10) + Derivative(x(t), (t, 2)),0) 
ics = {x(0): 0, Subs(Derivative(x(t), t), t, 0): 1} 
dsolve(ode,func=x(t),ics=ics)
 

\[ x{\left (t \right )} = \sin {\left (t \right )} + \frac {100 \cos {\left (\frac {9 t}{10} \right )}}{19} - \frac {100 \cos {\left (t \right )}}{19} \]