B0Bb`n itttt again!

Trig identities has to be my muddiest point. Another problem is, I'm not even sure what it is about it that I don't get, so I don't know what I need to work on. I'm not sure if it's remembering how to work out the trig identities or not. Kinda complicating. Mmm.. don't think there's much more I have trouble with. Oh.. one last thing is that there's a several questions I've been meaning to ask Mr. K about exercise 16, but haven't got the time to ask in class. So HELP MEEEEEEEE PLEASE, after lunch preferably, if you read this Mr. K. =D