A. (0, 2/3)

B. (0, 4/3)

C. (0, 1/3)

D. (0, 5/3)

The function f(x) = tan x has

f(x)= x-1/x is

The function f(x)=cot^{-1} x+x increases in the interval

The point P in the first quadrant of the ellipse x^{2}/8+y^{2}/18=1 so that the area of the triangle formed by the tangent at P and the coordinate axes is least

A rectangular sheet of dimensions 30 cm * 80 cm four equal squares of side x cm are removed at the corners, and the sides are then turned up so as to form an open rectangle box. The value of x, so that the value of the box is the greatest is