Learn why we get the area of a function by integrate it

[unseensoul]

For those who want to understand why the integration of a function gives the area of it, you can take a look at...

http://www.mathsroom.co.uk/downloads/Integration-Area_Under_A_Curve.ppt

I'm posting this because I think that not everyone who makes use of integration can really understand it. However, as it was very difficult to me to find such a good tutorial covering that aspect so well and clear, I am sharing it with those who are also interested in.

[fedaykin]

Why isn't this the first thing my book (James Stewart's Calculus, 5e) mentions in the section of finding the area under a curve?

Thank you