Evaluate and simplify cos 2pi/3. The options for answers are in the picture attachment, but I have NO idea how to get any of them? Please, Any help is appreciated (:

Evaluate and simplify cos 2pi3 The options for answers are in the picture attachment but I have NO idea how to get any of them Please Any help is appreciated class=

Respuesta :

Tareki
when pi is inside the trigonometric function you can subs. it by 180 degree 
so cos(2*180/3) = cos(120) = -0.5