(Trick Question: ) What is 0 **·** **u** ?

If the "0" is a scalar (which the non-bold type indicates) then this operation makes no sense.

If the "0" means the zero-vector (which means the zero should have been in bold face) then the result is the scalar 0.

The dot product is also defined for column matrices.

Leta= ( a_{1}, a_{2})^{T}

Letb= ( b_{1}, b_{2})^{T}

Then the dot product is defined as:

a · b= a_{1}b_{1}+ a_{2}b_{2}

Multiply corresponding elements of each column matrix, then add up the products. The result is a scalar value.

Sometimes the dot product
of column matrices is written like this: **a ^{T} b**
(but it is defined the same way).
The reason for this second, odd notation will be apparent in a later chapter
when matrix multiplication is discussed.

Here is an example:

**a**= ( 1, 2 )^{T}**b**= ( 3, 4 )^{T}**a · b**= 1*3 + 2*4 = 3 + 8 = 11

**a**= ( 1, 2 )^{T}**b**= ( 3, 4 )^{T}- What is:
**b · a**?