Answer:
Reference angle will be [tex]60^{\circ}[/tex]
[tex]cos(1680)=\frac{-1}{2}[/tex]
[tex]sin(1680)=-0.866[/tex]
Step-by-step explanation:
We have given [tex]cos(1680^{\circ})[/tex]
It can be written as [tex]cos(1680^{\circ})=cos(8\pi +240)[/tex]
As 240° is lie in the third quadrant
And we know that for third quadrant
Reference angle is given by [tex]angle-180^{\circ}[/tex]
So reference angle will be [tex]240^{\circ}-180^{\circ}=60^{\circ}[/tex]
Now [tex]cos(1640)=cos(9\pi +60)=-cos60=\frac{-1}{2}[/tex]
[tex]sin(1640)=cos(9\pi +60)=-sin60=-0.866[/tex]
