Question

How do you find the value of `cot ((2pi)/3)` using the double angle or half angle identity?

Answer 1

`ctg(2pi/3)=-1/(root2(3))`

Explanation:

`ctg(2pi/3)=cos(2pi/3)/sin(2pi/3)=(cos^2(pi/3)-sin^2(pi/3))/(2sin(pi/3)cos(pi/3))=`
`=(1/4-3/4)/(2*root2(3)/2*1/2)=-1/root2(3)`