-1

Is there an intuitive geometric proof to this?

1 Answers1

2

If a singular point of a tangent vector field $X$ means that $X(x)=0$, your assertion is not true. There exists parallelizable spheres, $S^1,S^3,S^7$ which are the only parallelizable spheres after results of Bott, Kervaire, Milnor.