Hi there.

We learned in calc the sum and difference identities:

For the most part it's not too bad, but I'm confused on a couple of problems in my book.

What would tan(a-b) be if sin a = .67, cos a = .74, sin b =.13 and cos b =-.99

The cos of b, if you notice, is negative.

how do I find tan(a + pi)?

what's cos (a + pi/3)?

and what's sin (pi/6 - a)?

Thanks a lot!