An insect crawls up a hemispherical surface very slowly. The coefficient of friction between the insect and the surface is 1/3. If the line joining the centre of the hemispherical surface to the insect makes an angle `alpha` with the vertical, the maximum possible value of is given by:

Explanation

`N=mg cos theta ` …..(1)
`mu N = mg sin theta` ……(2)
From (1) and (2) we get :
`cot theta = 1//mu = 3 rArr theta = cot^(-1)` (3).