"exercise 10.1 (Dr.W.Lindner)" -- This is only a little ('trivial') syntactic gym with EigenMath ;) "The solution .." x = A*cos(omega t) + B*sin(omega t) x ".. fullfills (10.8), because both sides gives equal results:" " x'=" d(x,t) " x''=" d(x,t,2) -- RHS equals " -w^2*x =" - omega^2 * x -- LHS check(- omega^2 * x == d(x,t,2)) "ok." Run