निम्न में मान ज्ञात करो (i) `cos (-60^(@))` (ii) `tan 210^(@)` (iii) `cos 120^(@)`

Options

A. `(i)=1/2` ,`(ii)=1/sqrt3`, `(iii)=-1/2`
B. `(i)=1/sqrt2` ,`(ii)=1/sqrt3`, `(iii)=1/2`
C. `(i)=1/2` ,`(ii)=1/sqrt3`, `(iii)=1/sqrt2`
D. `(i)=-1/2` ,`(ii)=-1/sqrt3`, `(iii)=1/sqrt2`

Answer

A

Explanation

(i) `cos(-60^(@))=cos 60^(@)=1/2`
(ii) `tan 210^(@)=tan(180^(@)+30^(@))=tan30^(2)=1/(sqrt(3))`


(iii) `cos 120^(@)=cos(180^(@)-60^(@))=-cos60^(@)=-1/2`