Solve Reflection & Refraction w/ Fermats Principle

[Morten1988]

Hey
I am working on a project about Ray tracing and I find myself stuck on 1 of the 5 questions my teacher has made.

Homework Statement

Explain how you can use Fermats principle to solve the formula of reflection and refraction.

Homework Equations

I do not now how I am going get from Fermats principle to a formula for reflection and refraction.

The Attempt at a Solution

I now that Fermats principle is: The path of a ray of light between two points is the path that minimizes the travel time.

I also know that the formula of refraction is:
Se picture

Now I can't get any father

Hope you can help me out a bit.
Regards
Morten

(sorry about my bad English but I am not native)

 

[Shooting Star]

Start with the reflection case, which is easier.

Draw a diagram for reflection light from one pt to another, and just think of what you have to prove to show that light travels the least distance from the 1st point to the other after touching the mirror. Write whatever comes to your mind.