Hi everyone (again - sorry...)
From your past experience, is it necessary to learn/memorize how to prove the angle sum identities for trigonometry? I'm referring to the sin(x+y) and so on...
It's easy to prove the double angle identities using the angle sum identities, so I can remember...
Hi everyone,
After much frustration, I have resulted to this forum to answer my question! It is 15)c) in the picture below.
Thanks in advance!
EDIT: I should have added I can get the obvious results of 30 and -150, but the answers say that it is also 0 and +-180