Perfectly Perpendicular?

My family is currently renovating the kitchen, and the workers just put in the tile backsplash. Supposedly they have tools to make sure they place the tile perfectly, but I decided to see if it actually aligned. Surely if the tile was placed perfectly, then there should be a perpendicular line in between the tiles.

By definition, a perpendicular line is one that has a right angle (which is 90 degrees) on both sides. However, when I measured the angles of the tiles, it looks like the tile guys were a little off. One side is about 90.29 degrees and the other side is 89.71 degrees. It's pretty close but not perfect. Sorry guys but I just proved you wrong....It still looks really good though! (~JC2)