Define oxygen dissociation curve. Can you suggest any reason for its sigmoidal pattern?

Define : Oxygen dissociation curve. Can you give reason for its sigmoid appearance ?

Can you give any two axioms from your daily life.

Can you find the surface area of sphere in any other way?

A plane electromagnetic wave travels in vacuum along z-direction. What can you say about the directions of its electric and magnetic field vectors? If the frequency of the wave is 30 MHz, what is its wavelength?