Arcsin(theta) = Arcsin(1/3) = theta = 19.47 degrees then just use calculator to find cot(19.47) = 2.828
Sorry ...didn't see 'EXACT' in your post
sin(theta) = 1/3 cos^2 (theta) = (1-sin^2)
= 1-1/9 = 8/9
cos theta = sqrt (8/9)= 2sqrt2 / 3
COT(theta) = cos/sin = (2sqr2 / 3) / 1/3 = 2sqrt2 / 3 x 3/1 = 2 sqrt2