Gymnosperms lack true fruits because.....

$\cos \left[\cos ^{-1}\left(-\frac{1}{7}\right)+\sin ^{-1}\left(-\frac{1}{7}\right)\right]$ is equal to

If Avogadro number $N_A$ is changed from $6.022 \times 10^{23} \ mol^{-1}$ to $6.022 \times 10^{20} \ mol^{-1}$,this would change:

The angle between the lines $x \cos \alpha_1 + y \sin \alpha_1 = p_1$ and $x \cos \alpha_2 + y \sin \alpha_2 = p_2$ is:

The sensitivity of a galvanometer is $60 \text{ division/A}$. When a shunt is used,its sensitivity becomes $10 \text{ division/A}$. If the galvanometer is of resistance $20 \ \Omega$,the value of shunt used is: (in $\Omega$)

Which of the following is a secondary pollutant?