How does Cos 5pi/6turn into -square root of 3 divided by 2Please explain why I am very confused. thank you

Question

asked Jan 22, 2023 204k views

1 Answer

Keshet · Answer 1 · 2023-01-26T12:17:46+0000

Cos 5π/6

Looking at the trigonometric unit circle:

Cos (-π/6+π) = -cos π/6

Looking at the trigonometric table of Special arcs:

-cos π/6= -√3/2