I think there still might be a typo. In the third line from the top, it should be
$$\sqrt{1 - \left(\frac{\eta_i}{\eta_t}\right)^2 \sin^2\theta_i}$$
(the change is $\theta_t$ to $\theta_i$)
@jezimmer. Thanks. You are correct, slide fixed. (you will need to refresh)
I think there still might be a typo. In the third line from the top, it should be
$$\sqrt{1 - \left(\frac{\eta_i}{\eta_t}\right)^2 \sin^2\theta_i}$$
(the change is $\theta_t$ to $\theta_i$)
@jezimmer. Thanks. You are correct, slide fixed. (you will need to refresh)