refraction of light !urgent!

Do you remember the formula of refraction?

Bsinb=Asina, where A and B are the refractive index of two medium and a,b are the corresponding angles.

Since the refractive index of air is almost 1, we can simpify the formula to
sinb=Asina, where b is the angle in air , a is the angle in medium X and A is the refractive index in medium X.

(sina) / (sinb) = 1/A
It is given that sina/sinb = 0.8,
the refractive index in medium X is 1/0.8 = 1.25.

If c is another angle in air, d is the corresponding angle in medium X,
1sinc=1.25sind
(sinc) / (sind) = 1.25



2010-11-21 00:10:10 補充：
I cannot input the symbol of your question in my answer. Hope that you can understand. If still find difficulties, feel free to ask.

take reciprical