Question: On a calm, bright day, you're scuba diving in a deep lake (n = 1.35), 5.40 m away from your sailboat in the horizontal direction. When you are 2.20 m below the surface, the top of the sailboat mast appears to you to be in a direction 31.0° from vertical.
Question 1: Calculate the height of the mast.
I know the correct answer but explain how to get this answer!