vertical angles

This i san image of blender blades, which have to do with the food industry. The blades are usually used for chopping up foods, they are not used as weapons in the upcoming Mission Impossible, so don't get confused. The purple lines represent vertical angles, meaning if they are the are on opposite sides and make an "X" looking thing. They are also congruent to each other.
http://www.alibaba.com/product-gs/203198523/blender_blade/showimage.html