Let K {\displaystyle {}K} be a field. For i ∈ { 1 , … , n } {\displaystyle {}i\in \{1,\ldots ,n\}} , let K {\displaystyle {}K} -vector spaces V i {\displaystyle {}V_{i}} and W i {\displaystyle {}W_{i}} , and linear mappings
be given. Show that the product mapping
is also a linear mapping between the product spaces.