You would probably have more luck in getting help if you showed the work you've done and where you get stuck.

For 6. make the substitution : .

Now make the substitution (a better one would involve a hyperbolic function but you said trig substitution so you're stuck with it): .

There are various ways of dealing with this last integral - a trick with algebra that makes it easy and the Weiestrass substitution that makes harder weather of it.

(You should check the details because I'm very careless).