kill(all);

fpprintprec:6;

      Problem from Simphiwe Pastor Dlamini
      Solve for y':
      y = cos(x)^(1/x)
      y''' + y'' = 0

f(x):=cos(x)^(1/x);

van=facebook.com/LearningCalculus$

diff(f(x),x);

g(x):= factor(fullratsimp(''(diff(f(x),x,3)+diff(f(x),x,2))))$

newton(t):=float(subst(t,x,x-g(x)/diff(g(x),x)));

newton(newton(5.92793));

newton(newton(-6.78348));