Question

whats is the value of theta , if
cos theta = -1/2

Answer 1

cos theta = -1/2
so theta = cos^-1 (-1/2)

Answer 2

let me use x instead of theta
cosx=-1/2
cosx=-cos(pi/3)
cosx = cos(pi- pi/3)=cos2(pi/3)

Answer 3

i.e cos x =cos 2(pi/3)
or x= 2(pi/3)