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Skill: Calculate the dot product of a matrix row and column

Explanation and Free Practice Resources

For finite matrices with real-number entries, a row and a column can be paired when they contain the same number of entries; their dot product is the sum of the products of corresponding entries. This scalar is one entry of a matrix product and captures how the values in the row combine with those in the column. Complex-valued and more abstract generalizations are beyond this treatment.

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Detailed Explanation: Calculate the dot product of a matrix row and column

To find the dot product of a row and a column, multiply the entries in matching positions, then add the products. They must have the same number of entries.

For example, find the product of the row

[2−13]\begin{bmatrix}2 & -1 & 3\end{bmatrix}

and the column

[45−2].\begin{bmatrix}4\\5\\-2\end{bmatrix}.
  1. Multiply corresponding entries: 2(4)2(4), (−1)(5)(-1)(5), and 3(−2)3(-2).
  2. Add the products:
2(4)+(−1)(5)+3(−2)=8−5−6=−3. 2(4)+(-1)(5)+3(-2)=8-5-6=-3.

The dot product is −3-3. It is a single number, and it could be one entry in a matrix product.

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    Matrices - Multiply - Two Matrices Single Row or Column to Values

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