The human body does not produce

The equation of the pair of tangents to the circle $x^2 + y^2 - 2x + 4y + 3 = 0$ from the point $(6, -5)$ is:

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.......$cm$.

The number of hydroxide ions produced by one molecule of sodium carbonate $(Na_2CO_3)$ on hydrolysis is

What is the $IUPAC$ name of the following compound?

What is microcosmic salt?