Hi this is regarding volume of solids, it's the basics but I can't get the answers and it's frustrating me! Any help will be very much appreciated, really!

1.) Find the volume of solid formed when y= is rotated for

I integrated from 1 to 3 and got 12pi units^3 as the answer, my answer after integration was pi( ..I can't see any possible errors in my working, I must have integrated wrongly..

2.) Find the volume of solid formed when y= is rotated for xE[1,3]

I integrated from 1 to 3.

I chose to use trig substitution, so I got

I had changed to since I thought , then ..

Simplifying, I ended up with

Also, I thought since , then

so I got ..

Separating into two integrals and changing tan to sec again, I ended up with

..

Integrating I got

, from 1 to 3..

Are my steps correct so far?

3.) A hemispherical bowl of radius 8cm is filled to a depth of 3cm. Find the volume of water in the bowl. The equation is

I integrated from 0 to 3, the equation ..

Please assist me I really am at a loss as to why my answers are all wrong..

Thank you very much!