Question: State an equivalent Trigonometric Ratio for each of the following

Question

a) cos π/16

b) sin 7π/9

c) tan 5π/4

d) sin 11π/6

My (attempted) answers are:

a) -cos π/16

b) sin 2π/9

c) tan π/4

d) -sin π/6

Are any of my attempted answers correct?

Answer 1

1. No, cos π/16 ≠ -cosπ/16, what you probably meant is cos π/16 = cos (-π/16)
2. yes
3. yes
4. yes