26.9.3 problem Exercise 22.3, page 240

Internal problem ID [7112]
Book : Ordinary Differential Equations, By Tenenbaum and Pollard. Dover, NY 1963
Section : Chapter 4. Higher order linear differential equations. Lesson 22. Variation of Parameters
Problem number : Exercise 22.3, page 240
Date solved : Tuesday, September 30, 2025 at 04:21:36 PM
CAS classification : [[_2nd_order, _linear, _nonhomogeneous]]

\begin{align*} y^{\prime \prime }+y&=\sec \left (x \right )^{2} \end{align*}

✓ Maple. Time used: 0.002 (sec). Leaf size: 23

ode:=diff(diff(y(x),x),x)+y(x) = sec(x)^2; 
dsolve(ode,y(x), singsol=all);
 

\[ y = \sin \left (x \right ) c_2 +\cos \left (x \right ) c_1 +\ln \left (\sec \left (x \right )+\tan \left (x \right )\right ) \sin \left (x \right )-1 \]

✓ Mathematica. Time used: 0.019 (sec). Leaf size: 28

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

\begin{align*} y(x)&\to 2 \sin (x) \text {arctanh}\left (\tan \left (\frac {x}{2}\right )\right )+c_1 \cos (x)+c_2 \sin (x)-1 \end{align*}

✓ Sympy. Time used: 0.181 (sec). Leaf size: 31

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

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