Answer:
I just learned this about a few weeks ago I hope this helps.
Explanation:
Since it's cosine you're only looking at Adjacent and the hypotenuse which the adj is 20 and the hyp is 25 so since cosine is adj/hyp you do 20/25 then simplify it to 20/25 divide both by 5 so it's simplified to 4/5.
Then you do Cos-1(4/5)=36.869 which is rounded to the tenth 36.9 but rounded to the hundredth 36.87.
Hope this helps