Use Snell's law to show fresnel Eq 1 can be expressed as Eq 2
Eq 1 = (ncosθ-n'cosθ') / (ncosθ+n'cosθ)
Eq 2 = (tanθ' - tanθ) / (tanθ' + tanθ)
nsinθ=n'sinθ' (Snell's law)
The Attempt at a Solution
n' = nsinθ / sinθ'
Substitute n' into equation and then multiply numerator and denominator by sinθ'/n gives:
(cosθsinθ'-cosθ'sinθ) / (cosθsinθ'+cosθ'sinθ)
I'm not sure how to get from here to Eq 2 though. I know sinθ/cosθ = tanθ and cosθ/sinθ=1/tanθ.