Question

Question #d532a

Answer 1

`sin((8pi)/3)=sqrt(3)/3`
`cos((8pi)/3)=-1/2`

Explanation:

`(8pi)/3=2pi and (2pi)/3`

`2pi` is full period and you can remove it.

SO, You have:
`sin((2pi)/3)`

You can use this:
`sin(pi-alpha)=sinalpha`
`cos(pi-alpha)=-cosalpha`

`sin((2pi)/3)=sin(pi-pi/3)=sin(pi/3)=sqrt(3)/3`
`cos((2pi)/3)=cos(pi-pi/3)=-cos(pi/3)=-1/2`