Why am I not understanding Pre-Calculus?

[TheDoll]

Ok just to let you guys know i am a straight A student when it comes to math. I always understood it and I never really had questions. Ever since i went into Honors Pre-Cal i feel like the math part of my brain died!! I don't understand what I'm doing most of the time I'm just guessing on how I do my work. Only a few things in that class I have understood. We've started this new chapter on Trigonometry and this circle thing that has to do with triangles and all these things with Pi and stuff like half of Pi or Pi over 3. I don't understand why I'm not getting it!! I have an A in the class right now but on my recent test i got an 83% usually i get 90% or higher. I don't know if its the math itself or my teacher but whatever it is I'm not getting it. It's so not understandable to the fact that i can't do my homework. WHAT DO I DO?!!!