# How to Derive Malus' Law

• I
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## Main Question or Discussion Point

Is there any source that how can I derive the Malus of ?
Where theres two polarizer

This is the equation
$$I_{out}=I_{in}[H_{90}+(H_0-H_{90})]cos^2(θ)$$

$H_0=1/2(k_1^2+k_2^2)$ and $H_{90} = k_1k_2$

Also I need to derive the $$I_{out}=1/2I_{in}cos^2θ$$ using integrals