Cork cambium is a

Match the following:

Column-$I$	Column-$II$
$(1)$ Oxytocin	$(p)$ Stimulates the secretion of thyroid hormone
$(2)$ Vasopressin	$(q)$ Act on the smooth muscles
$(3)$ $FSH$ and androgens	$(r)$ Stimulates resorption of water
$(4)$ $TSH$	$(s)$ Regulate spermatogenesis

An unpolarised light is incident at an interface of two dielectric media having refractive indices of $2$ (incident medium) and $2 \sqrt{3}$ (medium) respectively. To satisfy the condition that reflected and refracted rays are perpendicular to each other, the angle of incidence is . . . . . . .

The coordinates of the point $P$ on the curve $x=a(\theta+\sin \theta), y=a(1-\cos \theta)$,where the tangent is inclined at an angle $\frac{\pi}{4}$ to the $x$-axis,are

The pressure of an ideal gas varies with volume as $P = \alpha V$,where $\alpha$ is a constant. One mole of the gas is allowed to undergo expansion such that its volume becomes $m$ times its initial volume. The work done by the gas in the process is

The value of the series $\cos 12^{\circ} + \cos 84^{\circ} + \cos 132^{\circ} + \cos 156^{\circ}$ is