69.20.16 problem 655

Internal problem ID [18437]
Book : A book of problems in ordinary differential equations. M.L. KRASNOV, A.L. KISELYOV, G.I. MARKARENKO. MIR, MOSCOW. 1983
Section : Chapter 2 (Higher order ODEs). Section 15.5 Linear equations with variable coefficients. The Lagrange method. Exercises page 148
Problem number : 655
Date solved : Thursday, October 02, 2025 at 03:11:54 PM
CAS classification : [[_2nd_order, _linear, _nonhomogeneous]]

\begin{align*} y^{\prime \prime }+y&=\frac {1}{\cos \left (x \right )^{3}} \end{align*}

✓ Maple. Time used: 0.002 (sec). Leaf size: 19

ode:=diff(diff(y(x),x),x)+y(x) = 1/cos(x)^3; 
dsolve(ode,y(x), singsol=all);
 

\[ y = \left (-1+c_1 \right ) \cos \left (x \right )+\sin \left (x \right ) c_2 +\frac {\sec \left (x \right )}{2} \]

✓ Mathematica. Time used: 0.032 (sec). Leaf size: 25

ode=D[y[x],{x,2}]+y[x]==1/Cos[x]^3; 
ic={}; 
DSolve[{ode,ic},y[x],x,IncludeSingularSolutions->True]
 

\begin{align*} y(x)&\to -\frac {\sec (x)}{2}+c_1 \cos (x)+\sin (x) (\tan (x)+c_2) \end{align*}

✓ Sympy. Time used: 0.151 (sec). Leaf size: 22

from sympy import * 
x = symbols("x") 
y = Function("y") 
ode = Eq(y(x) + Derivative(y(x), (x, 2)) - 1/cos(x)**3,0) 
ics = {} 
dsolve(ode,func=y(x),ics=ics)
 

\[ y{\left (x \right )} = C_{1} \sin {\left (x \right )} + C_{2} \cos {\left (x \right )} - \frac {\cos {\left (2 x \right )}}{2 \cos {\left (x \right )}} \]