Dot product with vector and its transpose?
Solution 1:
The dot product "$\cdot$" is also known as scalar product and is defined as the sum of pairwise multiplication: $$\textbf v\cdot \textbf v = \sum_{i=1}^n\textbf v_i^2$$
The last part of the inequality is a matrix multiplication. Because of their dimension ($1\times n$ and $n\times 1$), the result will be $1\times 1$ but the result is exactly the same.