Last ones...

The Even/Odd identities are the ones that look simple, but it takes a bit of work to understand. You need to visualize the Unit Circle to understand these. You remember which quadrants each function are positive in, right? ASTC? STCA? TCAS? CAST? (depending on which quadrant you start in). Well, these functions deal with which functions are positive or negative depending on whether the degrees are positive or negative. Confusing right? That is why they don't explain it like that. They use the Identities, which are much simpler to understand. THe reason we even have these Identities, as supposed to a rule (If the degrees are negative, the answer is negative)  is because there is an exception that encompasses 1/3 of the total functions. Yep, cosine/secant have to be difficult. For them, it doesn't matter if the degrees are positive or negative. This is because they deal with X values. If the X value is negative, the answer is negative. and vice versa. How 'bout you just look at the Identities? That will make more sense than me giving you vague explanations.

Sin(-X)=-Sin(X)
Cos(-X)=Cos(X)
Tan(-X)=-Tan(X)
Cot(-X)=-Cot(X)
Sec(-X)=Sec(X)
Csc(-X)=-Csc(X)

And no, I don't know why they are called the Even/Odd Identities. If I had to guess, it would be because of the quadrant #s. If it was up to me they would be called the Positive/Negative Identities, as that is what they deal with.