(1) $a=g \cos \theta$
(2) $a=\frac{g}{\sin \theta}$
(3) $\mathbf{a}=\frac{\mathbf{g}}{\operatorname{cosec} \theta}$
(4) $a=g \tan \theta$
Solution:
Answer is (4)
In non-inertial frame we have,
$N \sin \theta=m a$
$N \cos \theta=m g \quad \ldots$ …(ii)
$\tan \theta=\frac{a}{g}$
$\mathrm{a}=\mathrm{g} \tan \theta$