Answer:
Reference angle will be [tex]60^{\circ}[/tex]
[tex]cos(840^{\circ})=-0.5[/tex]
[tex]sin(840^{\circ})=0.866[/tex]
Step-by-step explanation:
We have given [tex]cos(840^{\circ})[/tex]
Which can be written as [tex]cos(840^{\circ})=cos(2\pi +120)[/tex]
We know that 120° is present in second quadrant
We know that in second quadrant reference angle is given by [tex]180-angle[/tex]
So reference angle = [tex]180-120=60^{\circ}[/tex]
Now [tex]cos(840)=cos(2\pi +120)=-0.5[/tex]
And [tex]sin(840)=sin(2\pi +120)=0.866[/tex]
