Which of the following mixtures is known as fusion mixture?

If $z = \sec(y - ax) + \tan(y + ax)$,then $\frac{\partial^2 z}{\partial x^2} - a^2 \frac{\partial^2 z}{\partial y^2}$ is equal to

The diameter of a plano-convex lens is $6 \ cm$ and its thickness at the center is $3 \ mm$. If the speed of light in the material of the lens is $2 \times 10^8 \ m/s$,the focal length of the lens is.......$cm$.

Identify phenacetin from the following.

Which of the following contains both ionic and covalent bonds?

$A$ body is projected with a speed $u \ m/s$ at an angle $\beta$ with the horizontal. The kinetic energy at the highest point is $\frac{3}{4}$ of the initial kinetic energy. The value of $\beta$ is $....^{\circ}$