What is ∫ (dy)^2 ??? Fact: Let a<b. b ∫ (dy)2 = 0 a ===================== 1) First of all, I'm having trouble understanding the meaning of the above integral. I tried searching my elementary calculus textbooks, but I really couldn't find ANY integral like this. I have only seen integrals like ∫ (dy) in my calculus books and so I have no idea how they can have (dy)2 which makes no sense to me... 2) Why is the above fact true? How can we rigorously prove it? Hopefully someone can clarify this. Thank you!