values of two of the three expressions cos (x), sin (x), and tan (x), has not been set. Decide these values.

sin(x) = -((2)/(5^0.5)) , 3n/2<x<2n

cos(x)^2 + sin(x)^2 = 1

cos(x) = (1-sin(x)^2)^0.5 = (1-(-2/(5^0.5))^2)^0.5 = (9/5)^0.5

tan(x) = ((-2/(5^0.5))/((9/5)^0.5) = (-10^0.5)/5

When I leave it to my teacher I get error, does anyone know what the problem is? He says that you should show 3n/2<x<2n in sin, cos and tan in any way.

By n I mean pi