I worked it out myself. Everything is correct. I would add a couple of notes about part c: You might want to switch your calculator to radian mode if you used a calculator to find arctan (5/12) just to be on the safe side. IMHO, there is never really any reason to choose to work in degree mode unless a problem is written that way or the answer needs to be in degrees. Also, it seems like you used the diagram to obtain the exact value of sec2 [tex]\Theta[/tex]. That was a good choice (better than using any decimal approximation you obtained earlier). Also, not that it matters, but you could express 1/sec2 [tex]\Theta[/tex] as cos2 [tex]\Theta[/tex] if it would make it simpler for you to work with.
Everything was correct, but I wanted you to be able to see these things. Good Job.