Find the equation of the pair of straight lines that bisect the angles between the lines represented by $ax^2 + 2hxy + by^2 = 0$.

Which country produces the maximum amount of greenhouse gases?

$A$ liquid cools from $50^{\circ}C$ to $45^{\circ}C$ in $5 \ minutes$ and from $45^{\circ}C$ to $41.5^{\circ}C$ in the next $5 \ minutes$. The temperature of the surrounding is ......... $^{\circ}C$.

The value of $k$ for which the function $f(x) = \begin{cases} (\frac{4}{5})^{\frac{\tan 4x}{\tan 5x}}, & 0 < x < \frac{\pi}{2} \\ k + \frac{2}{5}, & x = \frac{\pi}{2} \end{cases}$ is continuous at $x = \frac{\pi}{2}$ is

$A$ water barrel having water up to a depth $d$ is placed on a table of height $h$. $A$ small hole is made on the wall of the barrel at its bottom. If the stream of water coming out of the hole falls on the ground at a horizontal distance $R$ from the barrel,then the value of $d$ is

$A$ prism of refractive index $\mu$ and angle $A$ is placed in the minimum deviation position. If the angle of minimum deviation is $A$,then the value of $A$ in terms of $\mu$ is :