La suite exacte de Mayer-Vietoris en cohomologie de Čech

We use explicit objects giving us an elementary algebraic treatment in a general nonnoetherian context, i.e. two finite sequences a̲, b̲ of a commutative ring and some Čech complexes built from these sequences. More precisely, our strategy consists in producing a short exact sequence of “type Čech“ complexes having the expected cohomologies. Then arises a simplicial complex on the set (a̲,b̲,ab̲) with a relatively surprising combinatory.