Do I need to know the double and half angle trig formulas for the Math II SAT Subject Test? What about other trigonometric identities?

**Trigonometric identities typically make up about four percent of the questions on the Math II SAT Subject Test, so you should know them if you're hoping to get a score in the 700 to 800 range.** Just don't spend too much time memorizing them since they make up such a small proportion of the test. Here's a list of trigonometric identities: http://www.sosmath.com/trig/Trig5/trig5/trig5.html. I would say that you can ignore the Sum-to-Product and Product-to-Sum sections, but the rest of the identities on the list are fair game for the test.

Source: http://www.sparknotes.com/testprep/books/sat2/math2c/chapter2section1.rhtml