Suppose cot = 3 in the 3rd quadrant.

I know that tan = 1/3 and than both sin and cos are negative, but i can't figure out what the values for them are.

I tried sin = 1/3cos and then

cos^2 + 1/9cos^2 = 1

cos^2 = 8/9

cos = -2sqrt(2)/3 but then i keep getting the wrong answer. Can someone help me find sin and cos please