Everything can be derived from cos(A + B) = ..... and sin(A + B) = .....Okay, so I have a possibly sort of unique situation!

My instructor does not give any identities or formulas for the tests, and while my final is a long ways off I need to do this at least once now that I'm done with this chapter.

This is a whopper, but I know that once I can see the relationships between them I'll have an easy time with it.

The sets of identities I need to be able to derive from scratch:

-Cosine, Sine, and Tangent of a sum or difference (6 identities)

-Double angle identities of a cosine (3 identities), sine (1) and tangent (1)

-( I have the cofunction identities, they're easy enough)

-Product to sum identities (4)

-Sum to product identities (4)

and lastly the half angle identities (5)

In total that's 30 identities, and I have 6 memorized so 24 identities I have to be able to derive to be able to use on my final exam. This is an online class ( tests are proctored ) and I am allowed to use my TI-89. ( That 'solve(' function is such a time saver )

I have all of the identities written down in my notes ( which are in notepad, so they're ugly. I have dysgraphia and taking written notes is an exercise in futility for me ) I've attached the text document with all my identities for this section

Where do I start? Which ones do I memorize and which ones do I derive?

However, derivations take time and may themselves require memorisation ....