I've derived the critical angle:
n1*sin(x1) = n2*sin(x2)
x1 is critical angle of incidence, call it C.
x2 is refracted at 90 degrees, therefore sinx2 = 1
so you get sinC = n2/n1.
However, in my syllabus it is written as sinC = 1/n
Can someone please explain to me how...