Nope, it's definitely meant to be x*x + y*y. It's "the root of x squared + y squared"... and there's no "power" operator in C#, so the easiest way of squaring something is just to multiply it by itself. (Your suggested code would multiply by 2, not take the value to the *power* of 2, which is different.)

My mistake. I was reading in the mobile, and "*" seems like "^".
I use R too , and in R "^" is a potency operator, but in c# is used for XOR.
I did read X^X + Y^Y (My wife is right, I really need Bifocals)