What will be the phase difference between virtual voltage and virtual current,when the current in the circuit is wattless (in $^o$)?

Which of the following hormones is not a secretory product of the human placenta?

The reason for the double helical structure of $DNA$ is the operation of

Four light sources produce the following four waves:
$(i)$ $y_1 = a \sin(\omega t + \phi_1)$
(ii) $y_2 = a \sin(2\omega t)$
(iii) $y_3 = d' \sin(\omega t + \phi_2)$
(iv) $y_4 = d' \sin(3\omega t + \phi)$
Superposition of which two waves gives rise to interference?

If a chord of the parabola $y^2=4x$ passes through its focus and makes an angle $\theta$ with the $X$-axis,then its length is

The angle between the curves $y=\sin x$ and $y=\cos x$ is