- #1

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I want to solve this Problem:

If M,N are manifolds then MxN is orientable iff M,N is orientable.

I have solved the direction "<=" This was no problem.

But i have a lot of problems to solve the other direction!

Let us assume that MxN are orientable.

Why has to be M,N be orientable?

We have defined orientable in different ways. Once per atlases and also with a differential non-vanishing form....

But i could't see a connection.

Can you please help me?

Regards