I have a question for physics about critical angles. It would be appreciated if you can help me out!

The question was to find the critical angle in the diagram below. I solved it in different ways, using different formulas (#1 and #2). But why is #1 wrong and #2 correct even though I used the correct formula for both?

N2 = 340 MS. - 12 air 6 2 = 900 less dense n, water More dense n,on2. . = 1500 m/s 2 Sin 90 - V 2 1500 siroc = 340 sorio = 3 4 . Senec Oc = arcsin 15 00 340 1500 ~ 13.1 V 1 1500 Oc = sin 340 V