Incorrect calculation of Euclidean distance on page

[dXu23]

On page 30, it says that sqrt((2 - 6)^(2) + (3 - 1)^(2)) = sqrt(18)

However, sqrt((2 - 6)^(2) + (3 - 1)^(2)) = sqrt((-4)^(2) + (2)^(2)) = sqrt(16 + 4) = sqrt(20) and

sqrt(18) <> sqrt(20)