Malus's Law?

Question

How is I =Io sin^2 (angle) related to Malus's Law:

I =Io cos^2 (angle)?

Io= intensity of polarized wave incident on the analyzer

Answer 1

There are two simple relations between these two formulas:

Io sin^2(angle) = Io - Io cos^2(angle)

Io sin^2(angle) = Io cos^2(90 deg - angle)

I have met the formula with sin used according to the second sense: sin was used instead of cos in the Malus' law because the angle measured was not in fact the angle between the polarizer's axes but 90 degrees minus that.

Of course, there are possible variations of the right hand side like using angle-90, 90+angle and so on, following from the properties of cos^2.