1) Try again. What is the "Reference Angle" for -5pi/3?

2) f(x) = cos(x) is an "Even Function"

2) h(x) = sin(x) is an "Odd Function"

2) What properties have odd and even functions?

3) No good. How did you get that?

That's enough of that. Please show your work and we can get started on setting you in the right direction.

5) I was going to gove it a rest, but then I saw "foil". Please forget you ever saw that term. Just learn to multiply.

cos(a-b) = cos(a)cos(b)+sin(a)sin(b)

cos(a+b) = cos(a)cos(b)-sin(a)sin(b)

Rather than try to work with all of this...

A = cos(a)cos(b)

B = sin(a)sin(b)

This gives...

cos(a-b) = A+B

cos(a+b) = A-B

Now what?