A few circle theorem questions (having a bit of trouble)

I have a sheet of questions on circle theorems. I did most of them but some of them I don't know what to do.

I know the basic rules:

1) The angle at the centre of the circle is double the angle at the circumference standing on the same arc

2) The angle in a semicircle is right angle or 90 degrees

3) Angles at the circumference of the circle standing on thee same arc are equal

4) The opposite angles of a cyclic quadrilateral are supplementary.

I haven't got up to tangent and chords yet. Just these for now.

http://i22.photobucket.com/albums/b319/jgv115/001.jpg

Thanks in advance!!