Hi,

I am confused as to why Type 1 double integration is dydx. As in the attached image, it seems that dx strips are taken first between a and b.

However, type 1 integration is dydx thus horizontal strips (dy) are taken first and then vertical dx strips between a and b. This I do not understand.

http://www.freeimagehosting.net/uploads/6417092e6e.jpg