Two orthogonal vectors

The two vectors in mathbf{R}^3:

 x = left(begin{array}{c} 1  1  3 end{array}right), ;; y = left(begin{array}{c} 4  -1  -1 end{array}right)

are orthogonal, since

 x^Ty =  underbrace{1 times 4}_{x_1 times y_1} +  underbrace{1 times (-1)}_{x_2 times y_2} + underbrace{(-1) times 3}_{x_3 times y_3} = 0.