What we learned in this week is to solve problems using SOH, CAH, and TOA. For example, on the problem, we already know what is the adjacent and the hypotenuse, so we can use cosine. We need to find what is a, so the way is

cos a = adjacent/hypotenuse

a = cos-1 adjacent/hypotenuse

The adjacent is 4 and the hypotenuse is 6.

a = cos-1 4/6

so, a is similar to 48.19