Find the value of cos 570

Please find below the solution to the asked query:

Cos 570$°$ =  Cos ( 360$°$ + 210$°$ ) =  Cos 210$°$                              ( We know Cos ( 360$°$ + a ) = Cos a )

Then,

Cos 210$°$ = Cos ( 180$°$ + 30$°$ ) = -  Cos 30$°$                                 ( We know Cos ( 180$°$ + a ) = - Cos a )

Then,

- Cos 30$°$ = - $\frac{\sqrt{3}}{2}$                                                                             ( We know Cos 30$°$ = $\frac{\sqrt{3}}{2}$ )

Therefore ,

Cos 570$°$ =  - $\frac{\sqrt{3}}{2}$                                                                            ( Ans )

Hope this information will clear your doubts about topic.