Radial symmetry is observed in:

In an acute angled triangle,$\cot B \cot C + \cot A \cot C + \cot A \cot B$ is equal to

$A$ solid sphere,a hollow sphere,and a ring are released from the top of an inclined plane (frictionless) so that they slide down the plane. Then,the maximum acceleration down the plane is for (no rolling):

$\int \frac{1+x+\sqrt{x+x^2}}{\sqrt{x}+\sqrt{1+x}} d x$ is equal to

$\int\left(\sqrt{\frac{a+x}{a-x}}+\sqrt{\frac{a-x}{a+x}}\right) d x$ is equal to

$A$ $p-n$ photodiode is made of a material with a band gap of $2.0\, eV$. The minimum frequency of the radiation that can be absorbed by the material is nearly