Integration application, force due to fluid pressure

[dimpledur]

Homework Statement

I'm working on a particular problem that involves the force on a face of a triangular prism under water. What I am wondering is if someone could explain how to find dA for the prism? If the prism is an equilateral triangle, then $$dA=\sqrt3dy$$ doesn't it? My book is showing that the area is $$2\sqrt3ydy$$ and I really cannot see how...

 

[dimpledur]

I understand that the thickness is sqrt(3)dy, but I can't seem to visualize how the width is 2y and thus dA=sqrt(3)2y dy