Question

can anyone explain some trigonometry for me?

mainly how to do this:
a)Use a sum or difference formula to calculate the exact value of sin( pi/12 ).
b) Use part a) to determine the exact value of cos(5pi/12 ).

Answer 1

pi/12=pi/3-pi/4 now use it

Answer 2

i must be tired...

Answer 3

cos(5pi/2)=cos(pi/2-pi/12)=sin(pi/12)

Answer 4

sin pi/3 cos pi/4 - cos pi/3 sin pi/4

Answer 5

yes