Distance Formula

Hey, I was doing the nodes tutorial on bit-101.com, a great tutorial by the way, and I was just wondering where this distance formula comes from. I understand x2 - x1 and y2 - y1, but where does that square root of dx^2 + dy^2 come from? Thanks!

		
dx = thingA._x - thingB._x;
dy = thingA._y - thingB._y;
dist = Math.sqrt(dx*dx+dy*dy);

http://www.cut-the-knot.org/pythagoras/index.shtml :wink:

also see:
http://www.kirupaforum.com/forums/showthread.php?s=&threadid=12181
and
http://www.kirupa.com/developer/actionscript/trigonometry.htm

AHH it’s obvious, im an idiot, thanks a lot though those links cleared it all up for me. Thanks again!