I am working on a problem that states:

In the rectangular coordinate system, are the points (r,s) and (u,v) equidistant from the origin.

The soluton starts by saying the distance from (r,s) and (0,0) is :
_______________
\/(r-0)^2+(s-0)^2


I undestand the origin is (0,0) but I dont understand how you arrive at the math above

Please help.

Thanks