Yes, those are correct. On 2.b, you may wish to add a label stating "substitution" where you used it. It is easy enough to follow, but you jump into it with no declaration, your instructor might not like this.
thanks for the reply.
yeah on 2.b, I kinda cut off my substitution of x=tan(ct) (left margin) when I scanned it so it should be fine.
Haha, I found a bubu on my 2.a this morning while in class. I forgot to carry down the 2 (should be 2cos+1 instead of cos+1), but all's well. I fixed it in the last sec.