`T sin theta = ma_(0)….(i), T cos theta =mg….(ii)`
dividing (i) & (ii) `tan theta = (a_(0))/(g)`
`:.` The string is making an angle `theta = tan^(-1) ((a_(0))/(g))` with the vertical equilibrium
Squaring and adding (i) and (ii)
`T^(2) sin^(2) theta +T^(2) cos^(2) theta =m^(2) (a_(0)^(2)+g^(2))`
`T =m sqrt(a_(0)^(2) +g^(2))` .