Finding the length of part of a curve.

Like the title of this thread suggests, I need to find the length of a section of the curve. I've done most of the questions but I got stuck on these ones:

http://i116.photobucket.com/albums/o...sproblem22.jpg

I'm clearly doing the polar co-ordinate ones incorrectly, and the parametric one has me slightly confused (are the limits t=at^2 and t=0?)(Worried)

If anyone can solve any of these it would be a great help!

If anyone wants I can post my work so far. It's just really long!

NOTE THAT 7 HAS BEEN DONE! =D