# State whether the expression is meaningful. If not, explain why? If so, state whether it is a vector or a scalar: abcd(a¯.b¯)×(c¯.d¯) - Mathematics and Statistics

Sum

State whether the expression is meaningful. If not, explain why? If so, state whether it is a vector or a scalar:

(bar"a".bar"b") xx (bar"c".bar"d")

#### Solution

This is meaningless because bar"a".bar"b", bar"c".bar"d" are scalars and cross product of two scalars is not defined.

Concept: Vectors and Their Types
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