because of range of pi we can conclude that teta is in third quadrant of x-y coordinate system which will determine us what is the sign of cos(teta) and tan(teta) cos(teta) = √(1-sin^2(teta)) = 1/2 but because teta is in third quadrant, cos(teta) has to be negative which means: cos(teta) = -1/2
tan(teta) = sin(teta)/cos(teta) = √3
tan of an angle that is in third quadrant is positive which is what we got.