How the *^&* do you solve this? Critical angle

So I had a science today on Optics. There was a question that I did not understand. In fact, nobody understood it because the teacher did not teach us it. It is about the index of refraction and the critical angle. Here is the question:

A diamond is dropped into an unknown liquid. From the angle that it is dropped, the angle that it is dropped at is a critical 52.4 degrees. What does the unknown substance most likely resemble?

BTW: diamond has an index of refraction of 2.42

I could not solve it because you usually have 3 pieces of info, but in this case you only had two: 2.42 and critical 52.4 degrees.

So basically what my question is, what is the unknown liquid and how would you solve for it?

sinΘc = n'/n

n' = sinΘc*n = sin52.4°*2.42 = 1.92

So, the unknown liquid is one that has an index of refraction of ~1.92