Answer:
Below in bold.
Step-by-step explanation:
Tan ( - 5π/4)
= tan (-5π/ 4 + 2π)
= tan (3π/4)
= -1.
sec π/ 3
= 1 / cos π/3
= 1 / 0.5
= 2.
cos 31π/ 6
= cos 5 1/6 π
= cos (5 1/6 - 4) π = 7π /6
= -√3/2.
